Concepts of CS Lecture 1

What is a computer?

Computer programs and algorithms A computer is a device that accepts inputs , processes data, and produces output according to a stored program . A computer program is a set of instructions written by a programmer using a programming language that tells a computer how to solve a problem or carry out a task. An algorithm is an abstract or a general procedure of instructions for solving a problem using the inputs followed by data processing and ending with the desired output.

Architecture of Modern Computer ALU ROM Input CU Output RAM Registers CPU Internal Memory External Storage

Central Processing Unit (CPU) The CPU of most modern computers are microprocessors, which is an electronic component that can be programmed to perform tasks (processing) on data it receives. CPU is the main unit of the computer which is responsible for executing the instructions stored in the internal memory. CPU includes: Arithmetic and logic unit (ALU): that performs all arithmetic and logical operations. Control unit (CU): it is responsible for controlling all the CPU operations including decoding the instructions stored in the main memory.

Internal Memory It is composed of chips of integrated crcuits which are cabable of storing and retreivng data quickly. Thee are two types of internal memory: Read Only Memory (ROM) Random Access Memory (RAM)

External Storage The space where data and programs are stored permanently even when the power is turned off. Nonvolatile external memory Magnetic tapes, magnetic disks, compact disks (CD), Flash memory, Floppy disk,

Computer Inputs

Computer Output

Computers types Computers ca be classified according to the size and computational space into: Super computers Mainframes computes Minicomputers Microcomputers

Personal Computers

Workstation Computers

Videogames are computers

Why computers sometimes called serves or clients? When a computer becomes a client? Which computer can be used as a server?

Super Computers the highest in speed The most expensive type Costs tens of millions of dollars Able to tackle complex tasks and Handle compute- intensive problems: Weather simulation and forecasting simulate Nuclear explosions Complex scientific applications.

Mainframe Computers A large size computer that is able to store huge amount of data. It supports hundreds to thousands of users simultaneously. It provides multitasking efficiently. The cost ranges from hundred thousand to millions of dollars.

Minicomputers They are similar to mainframes but on a smaller scale and less power. Such computers’ cost ranges from ten thousands up to several hundred thousands of dollars.

Microcomputer They are computers in which the CPU is manufactured as a single chip called “microprocessor” Compared with previous types, they are the lowest in power and cost. They include the following different types of computers: Personal computes Desktop computer Mobil or portable computer Notebook Tablet Ultra-mobile Handheld computers Workstations Videogames consoles

Numeric data epresentation

Text data representation

Text Data representation

ASCII Codes