A computer is a machine designed to perform

�A computer is a machine designed to perform certain tasks. � These tasks are specified with a set of instructions called a program. � Computer: programmable, electronic device that accepts data, performs operations, presents the results, and can store the data or results.

� Hardware and software: the two major components of any computer system Computer Hardware Software

� Physical (tangible) parts of a computer: �Internal: located inside the main system unit of the computer. e. g. : CPU, Main memory (RAM and ROM), hard disk �External: located outside the system unit and plug into connectors (ports) e. g. : Input/Output devices, such as keyboard, mouse, terminal/monitor, printer, external storage

� Input—entering � � � data into the computer Processing—performing operations on the data Output—presenting the results Storage—saving data, programs, or output for future use

e. g. Add two numbers

1. CPU 2. Main memory 3. Secondary storage 4. Input/Output devices

�Brain �Most of the computer expensive piece of hardware �Carries out arithmetic and logical operations

How does CPU work?

� Data that will be used in the � Temporary use � Faster access than storage near future Registers � Data immediately related to the operation being executed � Faster access than memory � Data that will � Long-term eventually be used

Main Types of Memory RAM: Random Access Memory ROM: Read Only Memory

RAM is volatile What is stored on RAM? � Operating System � Program currently running � Data needed by the program � Intermediate results waiting to be output

ROM is Non-volatile What is stored on ROM? � Instructions for booting the computer � Data and instructions can be read, but not modified � Instructions are typically recorded at factory

� Secondary storage: device that stores information permanently � Examples: �Hard disk �Flash drive �Floppy disk �CD-ROM

� Input devices feed data and programs into computers �Keyboard �Mouse �Secondary storage � Output devices display results �Monitor �Printer �Secondary storage

� Software: computer programs (set of instructions) that do specific tasks � System software: a program to operate and control the computer hardware and application programs �Operating system monitors the overall activity of the computer and provides services, such as: Memory management Input/output activities Storage management E. g. : Windows, Mac OS, Linux, Android, i. OS. � Application programs � Word processors � Spreadsheets � Games perform a specific task

� Programming: or software. the process of writing a program, Programming language: is a coded language that allows programmers to write instructions that the computer can understand perform specific actions. � code - (v) to write code, or to write instructions for a computer. � Event - An action that causes something to happen. � Program - An algorithm that has been coded into something that can be run by a machine. �