What is a computer?

A simple minded definition: a computer is a machine that computes. It has evolved from mechanical devices like the abacus and slide rule to the machine we know now that stores data (words, numbers, or pictures), interacts with external devices (the monitor, printer, speakers), and executes programs.

What is Programming?

A program is a set of instructions that a computer executes to achieve a certain desired effect - perform a calculation, render a picture, or produce music. A program is written in a specific programming language.

A computer cannot solve a problem by itself. The programmer must write down in minute details each step the computer has to take to solve the problem. An algorithm is the set of steps taken to solve a given problem.

What is an algorithm?

An algorithm is a step-by-step solution to a given problem. An algorithm has the following properties:

• finiteness - the process terminates, the number of steps are finite
• definiteness - each step is precisely stated
• effective computability - each step can be carried out by a computer

Why everyone should learn computer programming?

• Computers are ubiquitous. Programming is a basic skill like reading, writing, and arithmetic.
• Programming is a discipline that teaches the science and art of solving problems.
• Programming is different from using an application package like Microsoft Word or Excel. It allows you to tap the power of the computer for your own use.

Anatomy of a computer

• At the heart of the computer is the central processing unit (CPU). It consists of a single chip that is made out of millions of transistors. A simple processor (CPU) has the control circuits for fetching and executing instructions, an arithmetic logic unit for manipulating data, and registers for storing the processor status and a small amount of data. The CPU performs program control, arithmetic operations, and data transfers.
• A computer stores data and program instructions in memory (or main memory). The computer memory has some number of locations for storing. Associated with each location in memory is a unique binary number called the address. If there are n locations, then the address ranges from 0 to n-1. The primary storage is random-access memory (RAM) and read-only memory (ROM).
• Secondary storage is usually a hard disk that consists of rotating platters, that are coated with magnetic material, and have read/write heads.
• Removable storage is in the form of - floppy disks or diskettes, high capacity floppies like Zip disk, CDs, and DVDs. To store large amounts of data sometimes data tapes are used.
• Computers interact with the human user through the keyboard, the monitor, printer, and speakers.
• The CPU is mounted on a motherboard. The motherboard has the RAM, and card slots through which cards that control the external devices are connected. The CPU, RAM, the hard disk, and other devices are connected through a set of electrical lines called a bus.

Aside: Computer Arithmetic

A computer manipulates binary digits (bits). A bit can be either 0 or 1. A byte is 8 bits. 1 KiloByte is 1024 bytes. 1 MegaByte is 1024 KiloBytes. 1 GigaByte is 1024 MegaBytes.

• Decimal system
• Binary system
• Conversion from decimal to binary and vice versa
• Binary arithmetic
• Octal system
• Hexadecimal system

How does a computer run a program?

The program is first loaded into RAM. The computer reads the program one instruction at a time. As instructed the CPU reads data, manipulates it and stores it back. The CPU may also interact with the monitor, printer or speakers as instructed.