Transcript
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Introduction to computer & programming
Ms Sadia Ejaz
CS Department
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Computer ? ?
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The Four Equipment Functionsof a Computer System There are four main equipment functions of a
computer system:Input, Processing, Storage and Output
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The Four Equipment Functionsof a Computer System Input – the component through which a user instructs a
computer about what to do Processor – the engine that processes the instructions given by
the user Memory – where the processor stores information that is
required during its computations Storage – where information that is required to be used much
later is stored Output – the component that communicates the results of a
computation to the user
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Hardware/ Software Hardware - the "machinery" - computer
equipment - the CPU, the monitor, the keyboard, the mouse, the external speakers, the scanner, the printer, etc. The physical, touchable parts of a computer system.
Software - the program instructions that make the computer do some task, such as word process, manage databases, play games, etc.
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Hard Copy/Soft Copy
Hard Copy - a paper printout of the program code or data displayed on the screen.
Soft Copy - copy of a program stored on a hard drive, diskette, or CD.
Network - a hardware and software data communication system. Usually a group of computers that are linked to share memory and programs.
Control Unit - the unit inside of the CPU which "directs the traffic" - makes decisions. It performs the functions of fetch, decode, execute, and store.
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Data Structure Computer data is in what is called binary format. This means that
it is always a 0 or a 1. It only has these two states and must be in one of them.
There are several fundamental data units which include: Bit - A data unit which must be in one of the two binary states
described above. It is the smallest data unit that exists. Byte - 8 bits of data which has a possible value from 0 to 255. Word - Two bytes or 16 bits of data with a possible unsigned
value from 0 to 16535. Long word = 8 bytes = 64 bits Quad word = 16 bytes = 128 bits
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Bits, Bytes
KB 210 = 1024
MB 220 (over 1 million)
GB 230 (over 1 billion)
TB 240 (over 1 trillion)
Unit Symbol Number of Bytes
kilobyte
megabyte
gigabyte
terabyte
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All computers have the following essential hardware components:
INPUT PROCESSOR MEMORY
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INPUT
The devices used to give the computer data or commands are called Input devices. Includes keyboard, mouse, scanner, etc
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PROCESSOR
Central Processing Unit (CPU) The “brain” of the computer. This is the
component that actually executes instructions
Controls all other computer functions In PCs (personal computers) also called
the microprocessor or simply processor..
The processor is the logic of a computer
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Processor
Pentium Celeron Athlon PowerPC StrongARM (PDA) SPARC (Workstations)
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Arithmetic Logic Unit
It is the place where the actual execution of the instructions take place during the processing operation.
The data and instructions, stored in the primary storage before processing, are transferred as and when needed to the ALU, where processing takes place.
All ALU are designed to perform Four basic arithmetic operations Logic operations or comparisons, such as less than,
equal to, or greater than.
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Control Unit
It acts as a central nervous system for the other components of the computer system.
It manages and coordinates the entire computer system.
It obtains instructions from the program stored in main memory, interprets the instructions, and issues signals, which cause other units of the system to execute them.
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Storage Unit
Two types of storage: Primary Storage Secondary Storage
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Main memory holds information such as computer programs, numeric data, or documents created by a word processor.
All programs must be brought into main memory before execution.
When power is turned off, everything in main memory is lost Main memory is made up of capacitors. If a capacitor is charged, then its state is said to be 1, or ON. We could also say the bit is set. If a capacitor does not have a charge, then its state is said to be
0, or OFF. We could also say that the bit is reset or cleared
Main Memory (Primary Storage)
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Memory is divided into cells, where each cell contains 8 bits (a 1 or a 0). Eight bits is called a byte.
Each of these cells is uniquely numbered. The number associated with a cell is known
as its address. Main memory is volatile storage. That is, if
power is lost, the information in main memory is lost.
Main Memory (cont.)
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Secondary Storage Media (Secondary Storage) Provides permanent storage for information Retains information even when power is off Examples of secondary storage:
Hard Disks (sequential access) Floppy Disks (sequential access) Tapes (sequential access) CD-ROMs (random access) DVDs (random access)
Secondary storage media store files that contain computer programs data other types of information
This type of storage is called persistent (permanent) storage because it is non-volatile.
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Speed Primary storage is much faster to
access than secondary storage because of the proximity of the storage to the processor or because of the nature of the storage devices.
On the other hand, secondary storage can hold much more data than primary storage.
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Hard disk Hard disk is a computer storage
device which saves and retrieves the data when required. Its capacity is much greater than the computer memory (RAM, ROM). Data on hard disk is stored.
Today we can save huge amount of data on a single hard disk. Now hard disks can contain several billion bytes.
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CD A compact disc [sometimes spelled disk] (CD) is a small, portable, round medium for electronically recording, storing, and playing back audio, video, text, and other information in digital form.
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Floppy disk A diskette is a random access, removable
data storage medium that can be used with personal computers.
The term usually refers to the magnetic medium housed in a rigid plastic cartridge measuring 3.5 inches square and about 2 millimeters thick. Also called a "3.5-inch diskette," it can store up to 1.44 megabytes (MB) of data.
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DVD DVD (digital versatile disc) is an
optical disc technology that is expected to rapidly replace the CDROM disc (as well as the audio compact disc) over the next few years.
The digital versatile disc (DVD) holds 4.7 gigabyte of information on one of its two sides, or enough for a 133-minute movie.
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Storage Devices - Other USB drive
Very popular – 64-512 MB Tape drive
Similar to cassette tape Used for backup
Zip drive 100 MB to 2 GB capacity Everyday use and backup
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OUTPUT The devices to which the computer
writes data are called Output devices.
Often converts the data into a human readable form. Monitor and printer are output devices.
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ROM ROM is "built-in" computer memory
containing data that normally can only be read, not written to.
ROM contains the programming that allows your computer to be "booted up" or regenerated each time
you turn it on. Unlike a computer's random access memory (RAM), the data in ROM is not lost when the computer power is turned off.
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Types of ROM PROM
PROM stands for Programmable read only memory
In PROM chip , the user can write his own instructions but at once
If there is any error in writing the instruction the error can not removed from the PROM
The chip become unusable
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Types of ROM EPROM
Stands for erasable programmable read only memory
User can erase a instruction if any any error occurred
EEPROM Stands for Electronically Erasable
Programmable Read Only memory
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EXAMPLE
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