The Modern Digital Computer

This lecture on the Modern Digital Computer focuses on:

1. What a computer is
2. Three basic functions of a computer
3. How computers work
4. Why use computers
5. Types of computers

What is a computer?

Dell Desktop	Laptops	Apple Mac

A computer is an automatic, electronic data processing machine. It accepts data as input, transforms these data into information by executing a stored program. Based on this simple definition, a modern smartphone is also a computer. It is a special computer that allows you to use radio signals to send and receive voice and text messages, videos, graphs etc.

A computer is any machine that can be programmed to accept data (input), process or transform that input into useful information called output, and store it away in a secondary storage device such as a hard disk for later use. The processing of input into output is directed by the software but performed by the hardware.

A digital computer accomplishes its tasks by counting. Because of how digital computers work internally they are said to be bi-stable devices ( 0 or 1 ). Digital computers 'speak' the binary language. The binary language is the language of ones and zeros.

Three Basic Operations of Computers

A computer performs three basic operations. They are:

1. Arithmetic operations ( + addition, - subtraction, * multiplication, / division )
2. Logical or relational operators:

   Logical operators	Explanation
   >	greater than
   <	less than
   =	equal to
   >=	greater than or equal to
   <=	less than or equal to
   <>	not equal to

3. Storage and Retrieval operations

Whenever the response to a question is yes or no / true or false, this is the kind of response one would get from a logical operation. What is your response to the question- " Is one more than two ? " If I were to write a computer program to display the answer to this question. The processing performed on the data would be a logical operation.

How a computer works

A computer works in four steps:

1. Input: Input is the data before processing. It comes from the mouse, keyboard, microphone, scanner and other external sensors.
2. Processing : Processing is where input gets transformed into output. The computer's Central Processing Unit (CPU) is its brain, is responsible for executing instructions and performing mathematical and logical operations on the input data.
3. Output : Output is the final result after data processing. It can be anything from text, images, video, to sound and music.
4. Storage : The storage is how the computer retains input data and stores output for later use. The hard drive is used for long-term and mass data storage while the data set for immediate processing is stored temporarily in the Random Access Memory (RAM).

Why do we use computers?

1. A computer performs its operations very quickly
2. Computers are accurate
3. Computers work continuously while requiring little maintenance
4. Personal computers are becoming smaller and more powerful while they are more affordable
5. Computers are versatile. They can be used for business, education, communicating with others and entertainment

Types of computers

1. Analog computers
2. Digital or calssical computers
3. Hybrid computers
4. Quantum computers

Analog computers operate on continuous data. They are designed to measure input such as temperature, pressure, lengths, voltages, currents and speed. An analog machine is usually a special-purpose device, dedicated to a single task.

Digital computers operate on discrete data. They use bits to count data rather than measure. Everyday personal computers like the laptop computers and desktop computers are examples of digital computers.

Hybrid computers process both discrete and continuous data. They accept analog signals and convert them into a digital form before processing. The processors used at petrol stations to measure the flow of petrol convert continuous data into a digital form to output the price of the fuel.

Quantum computers use quantum bits or qubits rather than binary digits to store data. Just as a bit is the basic unit of information in a classical computer, a qubit is the basic unit of information in a quantum computer. Quantum computing is a new form of computing. Look at this youtube 10 minute video to get an idea about what quantum computing is.

Analog computers and quantum computers are outside the scope of these lessons. This site focuses on classical or digital computers only.

Test Yourself

Assignment 1.1

code : 01-004

1)   A traditional computer is made up of a processor with a single core. A core contains an _____ , ______ and registers.

2)    A _______ _____ is the sequence of instructions performed to execute one program instruction.

3)    A ________ is a temporary storage location that holds a single instruction or data item.

4)    The _______ determines the sequence in which instructions are executed.

5)    Data and instructions are sent to the _____ for processing .

6)   Computers are ubiquitous. What does that mean?