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 a computer system?

A complete computer system consists more than just a computer. The four main components are:

• Hardware - the physical computer
• Operating System - software that allows other pieces of software and human users to interact with the hardware
• Application Programs - specialized software like Word, Excel, Firefox
• End User - human user or another application program

What is the hardware?

• Case - desktop, mini tower, full tower
• Power Supply - Converts alternating voltage at 110 V to various direct voltage outputs like 12V, 5V, etc.
• Motherboard - Checks other hardware components, loads operating system, and controls data flow in the computer.
• Processor - Made out of millions of transistors and provides the computing power (arithmetic and logical functionalities)
• Memory - Temporary storage for operating system and application programs.
• Hard Drive - Permanent storage of software
• CD / DVD Drive - Secondary storage of programs and data
• Video Card - Converts data into a suitable format such that it can be displayed on the monitor
• Network Card - Receives and sends data to other comptuers on the network
• Sound Card - Converts data into a form such that it can be played through speakers or converts sound received to digital form
• Keyboard / Mouse - Allows human interaction with the computer
• Monitor - Visible display of computer output

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. It understands only machine language that is expressed in binary.
• 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, DVDs, and flash drives. 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 slots for the RAM, and other card slots for the video, network, and sound cards. The CPU, RAM, the hard disk, and other devices are connected through a set of electrical lines called a bus.

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

How does a computer run a program?

The program is first loaded into RAM. The computer reads the program one instruction at a time. The CPU decodes the instruction, reads data, executes the instruction and stores results (if any). The CPU may also interact with the monitor, printer, speakers or other peripheral devices as instructed.

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.

Aside - Computer Arithmetic

The unit of information in a computer is a bit. A bit is either 0 or 1. Eight bits make a byte. Storage capacity of either the RAM or Hard Drive is measured in bytes. The increments in capacity are in powers of 2 (2¹⁰ = 1024). Here are some commonly used units:

1 KiloByte (KB) = 210 Bytes (~ 103 Bytes)
1 MegaByte (MB) = 210 KiloBytes (~ 103 KB)
1 GigaByte (GB) = 210 MegaBytes (~ 103 MB)
1 TeraByte (TB) = 210 GigaBytes (~ 103 GB)
1 PetaByte (PB) = 210 TeraBytes (~ 103 TB)