Transcript
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INTRODUCTION TO COMPUTING
HANDOUT
BY
OSAIGBOVO TIMOTHY
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CHAPTER 1 WHAT IS A COMPUTER
A computer is an electronic device which is capable of receiving the inputs (data from the user),
storing it for a desired period of time, manipulating it according to the set of instructions (called
program) and producing the output to the user in desired form.
HISTORY OF COMPUTER
Calculating Machines (1400 BC): The first calculating device called ABACUS was developed by the
Egyptian and Chinese people. The word ABACUS means calculating board. It consisted of sticks in
horizontal positions on which were inserted sets of pebbles.
Napier’s bones: English mathematician John Napier built a mechanical device for the purpose of mul-
tiplication in 1617 A D. The device was known as Napier’s bones.
Slide Rule: English mathematician Edmund Gunter developed the slide rule. This machine could per-
form operations like addition, subtraction, multiplication, and division. It was widely used in Europe
in 16th century.
Pascal's Adding and Subtracting Machine: Blaise Pascal developed a machine at the age of 19 that
could add and subtract. The machine consisted of wheels, gears and cylinders.
Leibniz’s Multiplication and Dividing Machine: The German philosopher and mathematician
Gottfried Leibniz built around 1673 a mechanical device that could both multiply and divide.
Babbage’s Analytical Engine: It was in the year 1823 that a famous English man Charles Babbage
built a mechanical machine to do complex mathematical calculations. It was called difference engine.
Later he developed a general-purpose calculating machine called analytical engine. You should know
that Charles Babbage is called the father of computer.
COMPUTER GENERATIONS
The period, during which the evolution of computer took place, can be divided into five distinct phas-
es known as Generations of Computers. Each phase is distinguished from others on the basis of the
type of technology used.
ENIAC: It was the first electronic computer built in 1946 at University of Pennsylvania, USA by John
Eckert and John Mauchy. It was named Electronic Numerical Integrator and Calculator (ENIAC).
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SELF TEST 5 The hex numbering system has a base of ________, and the binary numbering system has a base of
________. The value of a particular digit in a number is determined by its relative position in a sequence of digits.
(T/F)
A single hexadecimal digit can represent how many binary digits: (a) two, (b) three, or (c) four?
The bases of the binary and decimal numbering systems are multiples of 2. (T/F)
The binary equivalent of a decimal 255 is ________.
The binary equivalent of a hexadecimal 1C is ________.
The decimal equivalent of a hexadecimal 1B6 is ________.
The hexadecimal equivalent of a decimal 129 is ________.
The decimal equivalent of a binary 110101 is ________.
The hexadecimal equivalent of a binary 1001 is ________.
The binary equivalent of a decimal 28 is ________.
The binary equivalent of a hexadecimal 35 is ________.
The decimal equivalent of a hexadecimal 7 is ________.
The hexadecimal equivalent of a decimal 49 is ________.
The decimal equivalent of a binary 110110110 is ________.
The hexadecimal equivalent of a binary 1110 is ________.
The result of 1012 + 112 is ________ (in binary).
The result of A116 + BC16 + 1016 is ________ (in hexadecimal).
The result of 6010 + F116 ‑ 10010012 is ________ (in decimal).
The result of 112 + 278 + 9310 ‑ B16 is ________ (in decimal).
Self‑test answers. 1. 16, 2. 2. T. 3. 4. 4. F. 5. 11111111. 6. 11100. 7. 438. 8. 81. 9. 53. 10. 9. 11. 11100.
12. 110101. 13. 7. 14. 31. 15. 438. 16. E. 17. 10002. 18. 16D16. 19. 22810. 20. 10810.
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Examples of Binary Arithmetic
Examples of Hexadecimal Arithmetic
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EDVAC: It stands for Electronic Discrete Variable Automatic Computer and was developed in 1950. The
concept of storing data and instructions inside the computer was introduced here.
Other Important Computers of First Generation
EDSAC: It stands for Electronic Delay Storage Automatic Computer and was developed by M.V. Wilkes at
Cambridge University in 1949.
UNIVAC: (UNIVersal Automatic Computer), the first electronic computer designed and sold to solve com-
mercial problems.
Limitations of First Generation Computer
Followings are the major drawbacks of First generation computers.
1. The operating speed was quite slow.
2. Power consumption was very high.
3. It required large space for installation.
4. The programming capability was quite low.
Second Generation Computers
Around 1955 a device called Transistor replaced the bulky electric tubes in the first generation computer.
Transistors are smaller than electric tubes and have higher operating speed. They have no filament and
require no heating. Manufacturing cost was also very low. Thus the size of the computer got reduced
considerably.
It is in the second generation that the concept of Central Processing Unit (CPU), memory, programming
language and input and output units were developed. programming languages such as COBOL, FORTRAN
were developed during this period.
Third Generation Computers
The third generation computers were introduced in 1964. They used Integrated Circuits (ICs). These ICs
are popularly known as Chips. Higher level language such as BASIC (Beginners All-purpose Symbolic In-
struction Code) was developed during this period. Computers of this generation were small in size, low
cost, large memory and processing speed is very high.
Fourth Generation Computers
The present day computers that you see today are the fourth generation computers that started around
1975. It uses large scale Integrated Circuits (LSIC) built on a single silicon chip called microprocessors.
Due to the development of microprocessor it is possible to place computer’s central processing unit
(CPU) on single chip. These computers are called microcomputers. Later very large scale Integrated Cir-
cuits (VLSIC) replaced LSICs.
Fifth Generation Computer
The computers of 1990s are said to be Fifth Generation computers. The speed is extremely high in fifth
generation computer. Apart from this it can perform parallel processing. The concept of Artificial intelli-
gence has been introduced to allow the computer to take its own decision. It is still in a developmental
stage.
CATEGORIES OF COMPUTERS
Broadly they can be divided it to the following categories.
Microcomputer: Microcomputer is at the lowest end of the computer range in terms of speed and stor-
age capacity. Its CPU is a microprocessor.
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Mini Computer: This is designed to support more than one user at a time. It possesses large storage
capacity and operates at a higher speed. The mini computer is used in multi-user system in which
various users can work at the same time.
Mainframes: These types of computers are generally 32-bit microprocessors. They operate at very
high speed, have very large storage capacity and can handle the work load of many users.
Supercomputer: They are the fastest and most expensive machines. They have high processing
speed compared to other computers. Supercomputers are mainly being used for weather fore-
casting, biomedical research, remote sensing, etc. Examples of supercomputers are CRAY YMP,
CRAY2, etc.
Palmtop/ Handheld/PDA: known as ‘organisers’, quite powerful software for their size, it is easy to
transfer data to a PC
Embedded Computers: Build into appliances such as TVs, microwaves, air conditioning system.
TYPES OF COMPUTER
We have three different kinds of computers:
i) Analog computers; ii) Digital computers and iii) Hybrid computers
Analog computers: These are devices that measure one form of physical quantities or another like
temperature, pressure, speed and so on. Examples of analog computers are thermometer, barome-
ter, speedometer and hygrometer
Digital computers: These are devices that are used for counting. Examples include adding
machine, billing machine, electronic wrist-watch and calculator
Hybrid computers: These devices combine the functions of measuring physical quantities as well as
counting. Electronic computers like desktop computers and notebooks are examples of hybrid com-
puters.
SELF TEST 1
1. State six advantages of computers over humans.
2. Distinguish between Microcomputer and Mainframe computer.
3. What is VLSIC?
4. Who is called the father of Computer Technology?
10. Define the following terms:
I) Computer II) Data III) Information IV) Program
CHAPTER 2 COMPONENTS OF A COMPUTER SYSTEM
Hardware: is any physical part of the computer that you can touch, see and pickup. E.g. monitor,
keyboard, mouse, disk drives, printer, scanner and speakers.
Software: refers to the set of computer programs that tells the computer what to do. We can say
that it is the collection of programs, which increase the capabilities of the hardware. Both have to
work together to produce meaningful result.
TYPES OF SOFTWARE
Application Software: Application Software is a set of programs to carry out operations for a specific
application. For example, payroll is an application software for an organization to produce pay slips
as an output.
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Hexadecimal to Binary
To convert hex numbers into binary, perform the grouping procedure for converting binary to hex in
reverse (see Figure 8).
FIGURE 8 Converting a Binary Number into Its Hexadecimal Equivalent
Place the binary digits in groups of four, then convert the binary number directly to hexadecimal.
Hexadecimal to Decimal
Use the same procedure as that used for binary‑to‑decimal conversions (see Figure 7) to convert hex
to decimal. Figure 9 demonstrates the conversion of a hex 3E7 into its decimal equivalent of 999.
FIGURE 9 Converting a Hexadecimal Number into Its Decimal Equivalent
Multiply the digits in a hexadecimal number by their position values.
ARITHMETIC IN BINARY AND HEXADECIMAL
The essentials of decimal arithmetic operations have been drilled into us so that we do addition and
subtraction al-
most by in-
stinct. We do
binary arithme-
tic, as well as
that of other
numbering sys-
tems, in the
same way that
we do decimal arithmetic. The only difference is that we have fewer (binary) or more (hexadecimal)
digits to use. Figure 10 illustrates and compares addition and subtraction in decimal with that in binary
and hex. Notice in Figure 10 that you carry to and borrow from adjacent positions, just as you do in
decimal arithmetic. As you can see, the only difference in doing arithmetic in the various numbering
systems is the number of digits used.
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CHAPTER FIVE
NUMBERING SYSTEMS AND COMPUTERS
We humans use a decimal, or base‑10, numbering system.
Computers operate in binary and communicate to us in decimal.
The decimal equivalents for binary, decimal, and hexadecimal num-bers are shown in Figure 1. We know that in decimal, any number greater than 9 is represented by a sequence of digits. When you count in decimal, you "carry" to the next position in groups of 10. As you ex-amine Figure 1, notice that you carry in groups of 2 in binary and in groups of 16 in hexadecimal. Also note that any combination of four binary digits can be represented by one "hex" digit. CONVERTING NUMBERS FROM ONE BASE INTO ANOTHER
Decimal to Binary or Hexadecimal
A decimal number can be converted easily into an equivalent number
of any base by the use of the division/remainder technique. This two‑step technique is illustrated in
Figure 5. Follow these steps to convert decimal to binary.
Use the two step division/remainder technique to
convert a decimal number into an equivalent number of
any base.
Step 1. Divide the number (19, in this example) repeated-
ly by 2, and record the remainder of each division
Step 2. Rotate the remainders as shown in Figure above;
the result (10011) is the binary equivalent of a decimal
19.
Figure 6 illustrates how the same division/remainder
technique is used to convert a decimal 453 into its hexa-
decimal equivalent (1C5). In a decimal‑to‑hex conver-
sion, the remainder is always one of the 16 hex digits.
Binary to Decimal and Hexadecimal
To convert from binary to decimal, multiply the 1s in a
binary number by their position values then sum the
products (see Figure 7). In Figure 7, for example, binary
11010 is converted into its decimal equivalent (26).
Converting
a Binary Number into Its Decimal Equivalent
Multiply the 1s in a binary number by their position val-
ues. The easiest conversion is binary to hex. To convert
binary to hex, simply begin with the 1s position on the
right and segment the binary number into groups of four
digits each (see Figure 8). Refer to the equivalence table
in Figure 2, and assign each group of four binary digits a
hex equivalent. Combine your result, and the conversion
is complete.
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System Software: may be defined as a set of one or more programs designed
to control the operation of computer system. It is not possible to run applica-
tion software without system software. Computer manufactures build and
supply this system software with the computer system. DOS, UNIX and WIN-
DOWS are some of the widely used system software.
Peripherals: A peripheral is any device which connects to the computer and
exchanges data with the CPU. Examples are: Monitor, keyboard, mouse, etc.
Central Processing Unit (CPU) :The CPU is the 'brain' of the computer. It is
where all the searching, sorting, calculating and decision making takes place.
The speed of the CPU is measured in either Megahertz (MHz) or more commonly now in Gigahertz
(GHz).
CPU Components: You need to have a basic understanding of the three main parts of a CPU. These
are the: Control Unit; Immediate Access Store; Arithmetic and Logic Unit (ALU)
The Control Unit
It controls and monitors the hardware attached to the system It controls the input and output of data
It controls the flow of data within the CPU
The Immediate Access Store or The Primary Memory
This holds the data and programs needed at that instant by the Control Unit.
The CPU reads data and programs kept on the backing storage and store them temporarily in the IAS's
memory.
Arithmetic and Logic Unit
This is where the computer processes data either by manipulating it or
acting upon it. It consists of two parts:
Arithmetic part - It performs the calculations on the data e.g. 3 + 2 =
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Logic part - this deals with logic and comparisons. For example, it
works out if one value is greater, less than or equal to another.
MOTHERBOARD
The Motherboard is the central circuit board of your computer. All of the components and peripherals
plug into it. The motherboard houses the ROM chips which store the BIOS instructions. RAM chips,
the CPU, the graphics card, sound card, network interface card, hard disk and various other external
ports and peripherals all attach directly to it.
DISK DRIVES
The purpose of a disk drive is to read data from a storage device. Common disk drives that you will
come across in your studies are: hard disk drive; removable hard disk drive; floppy disk drive; zip disk
drive; CD drive ;DVD drive .
INTERNAL MEMORY DEVICES
The two main types of computer internal memory that you need to clearly under-
stand are Random Access Memory (RAM) and Read Only Memory (ROM)
Read Only Memory (ROM)
Data stored on ROM is not erased when the power is switched off - it is permanent.
This is called 'non-volatile memory'. The ROM is used to hold data that cannot be changed by the us-
er. This data will usually be the software that tells the computer how to load the operating system
when it is switched on or re-booted.
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Random Access Memory (RAM)
RAM is volatile memory. The data is held on a chip, but only temporarily. The data
disappears if the power is switched off. If you save your work, it would be trans-
ferred from RAM to the hard disk where it would have been stored safely.
WHAT ARE REGISTERS?
Registers are temporary memory units that store words. The registers are located in the processor, instead of in RAM, so data can be accessed and stored faster. The eight registers in our example are called PC, AC, IR, TIR, +1, AMASK, MAR, and MBR, and are used as follows: Registers: PC: Program Counter. Stores the address of the instruction currently being executed.
AC Accumulator. Stores a previously calculated value or a value loaded from the main memory.
IR Instruction Register. Stores a copy of the instruction loaded from main memory. TIR Temporary Instruction Register. As the CPU evaluates exactly what an instruction is supposed to do, it stores the edited instruction in the TIR. 1 A constant that represents the number one. The CPU cannot access a number unless it is in a reg-ister or loaded from main memory, or somehow computed. Therefore this register is set aside to represent this often used number, AMASK Address Mask. When the CPU needs to know the address of a target word that an instruc-tion is using, the AMASK is AND'ed with the instruction to eliminate the opcode, leaving only the desired address.
MAR Memory Address Register. This register contains the address of the place the CPU wants to work with in the main memory. It is directly connected to the RAM chips on the motherboard.
MBR Memory Buffer Register. This register contains the word that was either loaded from main memory or that is going to be stored in main memory. It is also directly connected to the RAM chips on the motherboard.
AUXILIARY STORAGE DEVICES OR SECONDARY STORAGE
Most widely used secondary storage devices are magnetic tapes and magnetic disk.
1. Magnetic Tape: Magnetic tapes are used for large computers like mainframe computers where
large volume of data is stored for a longer time. The cost of storing data in tapes is inexpensive.
Advantages of Magnetic Tape:
Compact: A 10-inch diameter reel of tape is 2400 feet long and is able to hold 800, 1600 or 6250
characters in each inch of its length. The maximum capacity of such tape is 180 million characters.
Thus data are stored much more compactly on tape.
Economical: The cost of storing characters is very less as compared to other storage devices.
Fast: Copying of data is easier and fast.
Long term Storage and Re-usability: Magnetic tapes can be used for long term storage and a tape
can be used repeatedly with out loss of data.
Magnetic Disk: Data is stored on both the surface of the disk. Magnetic disks are most popular for
direct access storage device The information stored in a disk can be read many times without
affecting the stored data. So the reading operation is non-destructive. But if you want to write a
new data, then the existing data is erased from the disk and new data is recorded.
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CHAPTER 4 COMPUTER CODES, CHARACTER SETS AND DATABASE
Codes are used to represent the letters and special characters (such as +,-,*,$,&) in terms of 0’s and 1’s.
CHARACTER SETS
BCD - Binary Coded Decimal: BCD code is the simplest code to represent decimal numbers. In BCD code a
decimal number is represented by four binary bits. For example, 3 is represented as 0011.
ASCII - American Standard Code for Information Interchange: ASCII is pronounced as “ask-ee”.
It is widely used in micro computers. Micro computers using 8-bit word length use 7-bit to represent the
basic code and the 8th bit is used for parity or it may be permanently 0 or 1.
EBCDIC - Extended Binary Coded Decimal Interchange Code: It is pronounced as “ebb-see-dick”. It is
standard code in large computers. It is an 8-bit code without parity.
DATABASE
DEFINITION: A database is a collection of data or information which is held together in an organised or
logical way.
Tables
Databases store data or information in tables, just like the one below:
The table allows you to see all of the records stored in the database. Tables can store many records, from
a few dozen for a small database up to millions for a large company database.
Records
DEFINITION: A record is all of the data or information about one
person or one thing. In the table, all of the information about each
cartoon character is stored in a 'row' or 'record'.
Fields
DEFINITION: a 'field' is one piece of data or information about a person or thing.
SELF TEST 4
Give the full forms to the following
1. BCD 2. ASCII 3. EBCDIC 4.
2.Define the following database terms:
1.Database 2. File 3.Records 4.Fields 5.Primary key
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ADVANTAGES OF USING FLOWCHARTS The benefits of flowcharts are as follows: 1. Communication: Flowcharts are better way of communicating the logic of a system to all concerned. 2. Effective analysis: With the help of flowchart, problem can be analyzed in more effective way. 3. Proper documentation: Program flowcharts serve as a good program documentation, which is need-ed for various purposes. 4. Efficient Coding: The flowcharts act as a guide or blueprint during the systems analysis and program development phase. 5. Proper Debugging: The flowchart helps in debugging process. 6. Efficient Program Maintenance: The maintenance of program becomes easy with the help of flowchart. It helps the programmer to put efforts more efficiently on that part. Example of a flowchart:
Problem 1: Write an algorithm and draw the flowchart for finding the average of two numbers
Algorithm:
Input: two numbers x and y
Output: the average of x and y
Steps:
1. input x
2. input y
3. sum = x + y
4. average = sum /2
output average
Problem 2:
Develop a flowchart to sort
two numbers in ascending order.
Algorithm:
Steps:
1. input x
2. input y
3. is x > y?
4. if yes, display y then x if no, display x then y.
SELF TEST 3
1. Differentiate between machine language and Assembly language. 2. What is computer Language? 3. What is machine language? Why is it required? 4. What are advantages and disadvantages of machine language . 5. What is assembly language? What are its advantages over machine languages? 6. What is the difference between source program and object program? 7. What is higher level languages? Why are higher level languages are easier to use. 8. What is compiler? Why is it required? 9. What is interpreter? How does it differ from compiler? 10.Draw a flowchart for a program that input any two numbers. The program compares the number and reports which one is greater. 11. Develop an algorithm and a flowchart that will compute the area of a triangle.
PROBLEM 2 PROBLEM1
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Floppy Disk: It is similar to magnetic disk discussed above. It is cheaper than any other storage devices
and is portable. The floppy is a low cost device particularly suitable for personal computer system. It is
now obsolete.
Optical Disk: It is the necessity to store large volume of data that has led to the development of optical
disk storage medium. Optical disks can be divided into the following categories:
Compact Disk/ Read Only Memory (CD-ROM): CD-ROM disks are made of reflective metals. Here the
storage density is very high, storage cost is very low and access time is relatively fast. Each disk is ap-
proximately 4 1/2 inches in diameter and can hold over 600 MB of data. As the CD-ROM can be read
only we cannot write or make changes into the data contained in it.
Digital Versatile Disk (DVD): A DVD is similar to a CD in that it is an optical device and that a laser is
used to store the data and read the data. A single sided DVD can store about 4.7Gb of data. DVDs which
store data on both sides can hold over 9Gb of data.
Flash Memory: Flash memory storage devices are typically small, lightweight, removable and rewrita-
ble. Memory sticks are available from 1 Gb up to 8 Gb.
Advantages
They are more compact and portable than floppy disks or CDs/DVDs.
They hold more data than a floppy disk and nowadays often more than a CD.
They are more reliable than a floppy disk because they have no moving parts
Disadvantages
At the moment, the cost per megabyte of storage is more expensive than floppy disks, CDs or DVDs.
They can be easily lost
INPUT DEVICES
These are devices that are used to capture data and send it to a computer.
MANUAL INPUT DEVICES
Keyboard: to enter words and figures.
Touch screen: for making selections by touching the screen.
Mouse: to select icons to run programs or select, drag or move objects.
Tracker ball: For use by people with limited motor skills e.g. people with disabilities
Joystick: Used by a pilot to fly an aero plane or flight simulator.
Touch Screen: Selecting from a limited list of options
Scanner : Entering hard copy images into a computer
Digital Camera: Taking photographs for input to computers, for input to Photo printers
Microphone: Recording of voices for presentation software
Web Cams: To input moving pictures from a fixed position into a computer
AUTOMATIC INPUT DEVICES
Magnetic Ink Character Recognition: (MICR) To input magnetic characters, such as those found on bank
cheques
Optical Mark Reader (OMR): To input pencil marks on a form such as a school register.
Optical Character Recognition (OCR): To input text to a computer ready for processing by another soft-
ware package such as word processors,etc.
Barcode Reader: To input code numbers from products at a POS terminal, library books and member-
ship numbers
Magnetic Stripe Reader: At POS terminals, ATMs and in security applications
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ABACUS NAPIER BONE
SLIDE RULE
PASCAL MACHINE
LIEBNITZ MACHINE
BABBAGE ANALYTICAL ENGINE
TRANSISTOR
VACUUM TUBES
MECHANICAL CALCULATOR
ARTIFICIAL INTELLIGENCE
INTEGRATED CIRCUIT (IC)
VERY LARGE INTEGRATED CIRCUIT (VLIC)
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Introduction to flowcharts A flowchart is a graphical representation of an algorithm. These flowcharts play a vital role in the pro-gramming of a problem and are quite helpful in understanding the logic of complicated and lengthy problems. Once the flowchart is drawn, it becomes easy to write the program in any high level lan-guage. Often we see how flowcharts are helpful in explaining the program to others. Hence, it is correct to say that a flowchart is a must for the better documentation of a complex program. Symbols used in flowcharts:
Guidelines while drawing a flowchart:
The following are some guidelines in flowcharting:
a. In drawing a proper flowchart, all necessary requirements should be listed out in logical order.
b. The flowchart should be clear, neat and easy to follow. There should be no ambiguity in under-
standing the flowchart.
c. The usual direction of the flow of a procedure or system is from left to right or top to bottom.
d. Only one flow line should come out from a process symbol.
or
e. Only one flow line should enter a decision symbol, but two or three flow lines, one for each pos-sible answer, should leave the decision symbol.
f. Only one flow line is used in conjunction with terminal symbol.
h. If the flowchart becomes complex, it is better to use connector symbols to reduce the number
of flow lines. Avoid the intersection of flow lines.
i. Ensure that the flowchart has a logical start and finish.
j. It is useful to test the validity of the flowchart by passing through it with a simple test data.
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Disadvantages:
1. One of the major disadvantages is that assembly language is machine dependent. A program written
for one computer might not run in other computers with different hardware configuration.
HIGH LEVEL LANGUAGES High level languages are simple languages that use English and mathematical symbols like +, -, %, / etc. for its program construction. High level languages are problem-oriented languages because the instructions are suitable for solving a particular problem. There are mathematical oriented languages like FORTRAN (Formula Translation) and BASIC (Beginners All-purpose Symbolic Instruction Code) where very large processing is required. Advantages of High Level Languages Higher level languages have a major advantage over machine and assembly languages that higher level languages are easy to learn and use. It is because that they are similar to the languages used by us in our day to day life.
LANGUAGE TRANSLATOR ASSEMBLER An assembler is a program which is used to translate an assembly language program into machine-level equivalent. The program in assembly language is termed as source code & its machine language equiva-lent is called object code. COMPILER It is a program translator that translates the instruction of a high level language to machine language. It is called compiler because it compiles machine language instructions for every program instructions of higher level language. It scans the entire program first and then translates it into machine code. The programs written by the programmer in high level language is called source program or code. After this program is converted to machine languages by the compiler it is called object program or code. Higher Level Language --> (Compile) ---> Program --> Machine Language Program INTERPRETER An interpreter is another type of program translator
used for translating high level language into machine
language. It takes one statement of high level lan-
guages, translate it into machine language and immedi-
ately execute it. Translation and execution are carried
out for each statement. The advantage of interpreter
compared to compiler is its fast response to changes in
source program. It eliminates the need for a separate
compilation after changes to each program. Interpreters are easy to write and do not require large
memory in computer. The disadvantage of interpreter is that it is time consuming method because each
time a statement in a program is executed then it is first translated. Thus compiled machine language
program runs much faster than an interpreted program.
ALGORITHM AND FLOWCHARTS Algorithms: Algorithm is a step by step procedure to solve a particular problem. Before any problem can be solved using a computer, the person must familiarize himself with the problem & with the way in which it has to be solved.
Characteristics / Properties of an Algorithm: Finiteness: An algorithm should terminate (stop) after a finite number of steps. Definiteness: An algorithm should be simple, precisely defined i.e. the steps must be not be repeated creating confusion. Generality: An algorithm should be able to solve all problems of a particular type (for all inputs) for which it is designed.
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MAINFRAME COMPUTER LAPTOP COMPUTER
PERSONAL DIGITAL ASSISSTANT PERSONAL COMPUTER
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FUNCTIONS OF OPERATING SYSTEMS
1. Starting a computer
Booting – the process of starting or restarting a computer
Cold boot – turning on a computer that has been turned-off completely/properly
Warm boot – process of using the operating system to restart a computer
2. Providing user interface: You interact with software through its user interface. The user interface controls how you enter data and instructions and how information is displayed on the screen. 3. Managing programs: Single user/multitasking operating systems allow a user to use more than one program in a computer at one time 4. Managing memory: The purpose of memory management is to optimize the use of random access memory (RAM). 5. Scheduling jobs: The operating system determines the order in which jobs are processed. 6. Configuring devices: A driver, short for device driver, is a small program that tells the operating sys-tem how to communicate with a specific device 7. Providing file management and other utilities 8. Controlling a network 9. Administering security
TYPES OF OPERATING SYSTEM
Command-line Interface – text only
Menu-driven interface – text and menus Graphical user interface – buttons, text, images, animated elements EXAMPLES OF OPERATING SYSTEM
DOS; Windows XP; Mac OS X: Linux: Palm OS: Symbian OS VIRUSES AND ANTIVIRUS PROGRAMS
COMPUTER VIRUS
A computer virus is a potentially damaging computer program that affects or infects a computer nega-tively by altering the way the computer works without the user’s knowledge or permission. The pro-grammer of a virus is known as a virus author. Antivirus programs protect the computer against viruses by identifying and removing any computer
virus found in the memory, on storage media, or on incoming files. Ex. McAfee Virus Scan, Norton Anti-
virus.
SIGNS OF A VIRUS INFECTION:
An unusual message or image is displayed on the computer screen An unusual sound or music plays randomly The available memory is less than what should be available A program or file suddenly is missing An unknown program or file mysteriously appear 1. Write True or False:
(a) Secondary memory is called Auxiliary memory. (b) The magnetic tapes and magnetic disk are primary memories. (c) A CD-ROM is read only memory. (d) Mouse is an output device. (e) Printer is an important output device.
2. Which of the following do you think is hardware and which is software Keyboard, Floppy Disk, Visual Display Unit, Mouse, Central Processing Unit, Word Processor, Oper-
ating System, Joystick, Spreadsheet, Database
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CHAPTER 3 TYPES OF COMPUTER PROGRAMMING LANGUAGE AND TRANSLATORS
WHAT IS LANGUAGE?
It is a system of communication between you and me. Some of the basic natural languages that we are
familiar with are English, Hindi, etc. Your computer will not understand any of these natural languages
for transfer of data and instruction. So there are programming languages specially developed so that
you could pass your data and instructions to the computer to do specific job. You must have heard
names like FORTRAN, BASIC, and COBOL etc. These are programming languages. So instructions or pro-
grams are written in a particular language based on the type of job. As an example, for scientific applica-
tion FORTRAN and C languages are used. On the other hand COBOL is used for business applications.
PROGRAMMING LANGUAGES
There are two major types of programming languages. These are Low Level Languages and High Level
Languages. Low Level languages are further divided in to Machine language and Assembly language.
Low Level Languages
The term low level means closeness to the way in which the machine has been built. Low level lan-
guages are machine oriented.
(a) Machine Language
Machine Language is the only language that is directly understood by the computer. It does not need
any translator program. We also call it machine code and it is written as strings of 1's (one) and 0’s
(zero). For example, a program instruction may look like this: 1011000111101.It is not an easy language
for you to learn because of its difficult to understand. It is efficient for the computer but very inefficient
for programmers. It is considered to the first generation language.
Advantage
The only advantage is that program of machine language run very fast because no translation program
is required for the CPU.
Disadvantages
1. It is very difficult to program in machine language. The programmer has to know details of hardware
to write program.
2. The programmer has to remember a lot of codes to write a program which results in program errors.
3.It is difficult to debug the program.
(b) Assembly Language
It is the first step to improve the programming structure. You should know that computer can handle
numbers and letter. Therefore some combination of letters can be used to substitute for number of ma-
chine codes. The set of symbols and letters forms the Assembly Language and a translator program is
required to translate the Assembly Language to machine language. This translator program is called
`Assembler'. It is considered to be a second-generation language.
Advantages:
1.The symbolic programming of Assembly Language is easier to understand and saves a lot of time and
effort of the programmer.
2. It is easier to correct errors and modify program instructions.
3. Assembly Language has the same efficiency of execution as the machine level language. Because this
is one-to-one translator between assembly language program and its corresponding machine language
program.
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