Lecture 1

Lanie P. PaladInstructor

A computer is a general purpose device that can be programmed to carry out a finite set of arithmetic or logical operations.

The first electronic digital computers were developed between 1940 and 1945. Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs).[1] In this eramechanical analog computers were used for military applications.

Limited-function early computersThe history of the modern computer begins with two separate technologies, automated calculation and programmability. However no single device can be identified as the earliest computer, partly because of the inconsistent application of that term. A few devices are worth mentioning though, like some mechanical aids to computing, which were very successful and survived for centuries until the advent of the electronic calculator, 

First Generation Computer1951-1959

UNIVAC- The fist commercial computer developed in 1951, it was marked the beginning of the first generation. The major innovation then was the use of vacum tubes in place of relays as a means of storing data in memory and the use of stored-program concept.

Second Generation Computers 1959-1964

Solid state componets (transistors and diodes) and magnetic core storage formed the basis for the second generation computers. The transistor performs the same functions as a vacum tube except that electrons move through solid materials than a vacum tube. In this generation computers become much smaller in size, faster, more reliable and much greater in processing capability.

Third Generation Computers 1965-1970Integrated solid-state circuitry, improved secondary

storage devices and new input/output devices were most important advance of this generation. IBM ushered in the third generation when it announced the System/360 family.

Fourth Generation Computers

1970- Present

The major innovations were in the development of microeletronics and in the development of different areas in computer technology such as multiprocessing , multiprogramming, time sharing , operating speed and virtual storage.

Classification of Computers

Classification by Purpose a. General –Purpose Computers– This

machines have the capability of dealing with the variety of different problems, and are able to act in response to programs created to meet different needs. A general-purpose computer is one that has the ability to store different programs of instructions thus to perform a variety of operation.

b. Special- Purpose Computers- A special-purpose computer, as the name implies, is designed to perform one specific tasks. The program of instructions is built into, or permanently stored in, the machine. They are frequently referred to as “dedicated “ because of their limitations to the performance of the specific task at hand.

•Classification by type of data handleda. Analog Computers- The name analog comes from

the word “analogous” meaning similar. Analog computers are used for scientific, engineering and process control purposes. Because they deal with quantities that are continuously variable, they give only approximate results. The classic example of an analog device is the speedometer of an automobile.

b. Digital Computers- These are the machines that specialized in counting. It operates by counting values that are discrete or separate and distinct. Digital computers are used for both business data processing and scientific purposes.

c. Hybrid Computers- Although both analog and digital computers are extensively used and widely accepted in various industries,

manufacturers have attempted to design a computer that combines the best features of both types. Among the applications are space vehicle simulations and training of space pilots, analysis of signal received from special sensors attached to human and animals in laboratories and the solving of differential equation for chemical reactors.

Hardware - The hardware consists of tangible components, such as the main unit , monitor keyboard, printer contains slots for the insertion of various cards, and CPU (Central Processing Unit), which is like human brain.

Software – Unlike the hardware, software is like intangible recorded information, which we commonly refer to as programs, operational

programs, or applications. It consist of systems software and application software.

Peopleware- it represents the personnel involved in systems analysis, programming, computer operations, system maintenance and the like.

Word Processing- In the past, you may have to write out documents by hand or using a typewriter , but now , by using a computer you can create documents quickly and easily.

Real Time Communication – Internet enables you to communicate with people from far away in real time

Multimedia- It consist of music, music videos and movies and favorite television shows that you can possible enjoy right on you computer.

Bit – Fundamental unit of memory, which can be either 0 or 1.

Byte – The actual data processing unit (1byte=8 bits)

Kilo Byte 1KB 1,024 BytesMega Byte 1MB 1,048, 567 BytesGiga Byte 1GB 1,073,741,824 BytesTera Byte 1TB 1,099,511,627,776 Byte

The Computer SystemsCentral Processing UnitInput /Output unit Auxiliary or secondary storage unit

CPU- All operations performed by the computer system are controlled by the physical device called the CPU. It is also refer as the brains of the computer.

Input/Output Units –feed data into and retrieve data from the CPU. When inputting they convert the data, which are recorded in some medium, into a string of electrical impulses which are transmitted to the CPU for processing. Output devices write processed information for the user on request.

Storage Devices - Computer installations use a variety of auxiliary storage devices. The most commonly used are magnetic tape units, magnetic disk unit and magnetic drum units. The choice of such devices will depend to a large degree on the type of processing operations involved.

a. Magnetic tape units- It is the most popular sequential storage medium, used for storing high volume data that is typically processed in a batch mode and is used both for input/output data

Magnetic Disk Unit- It is the most popular random access storage m medium. Magnetic- disk mass storage units are classified into three types. (1) disks are fixed (2) disk can be removed into a form of disk pack (3) floppy disk.

Magnetic Drum – This is another type of random -access secondary storage device. It was used in third generation and early fourth generation computer. This device is not versatile and now being phased out.

Computers Capabilities

1. Ability to perform certain logic operations.2. Ability to provide new time dimensions.3. Ability to store and retrieve information.4. Ability to control error.5. Ability to check itself.

Computer Limitation

1. Dependence on prepared instructions2. Inability to derive meaning from objects.3. Inability to generate information.4. It cannot correct wrong instructions.

Why computer sometimes fail?

1. Input errors2. Errors in instructing a computer3. The communication gap4. Improper controls5. Lack of standards6. Lack of adequate manufacturer support.