Lecture notes Programming for C

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UNIT I
INTRODUCTION

Evolution of Programming & Languages - Problem solving through programming - Writing
algorithms & Pseudo code - Single line and multiline comments - Introduction to C: Structure of
the C program - Input and output statements. Variables and identifiers, Constants, Keywords -
Values, Names, Scope, Binding, Storage Classes - Numeric Data types: integer, floating point,
Non-Numeric Data types: char and string - L value and R value in expression, Increment and
decrement operator - Comma, Arrow and Assignment operator, Bitwise and Size-of operator -
Arithmetic, Relational and logical Operators - Condition Operators, Operator Precedence -
Expressions with pre / post increment operator.


Introduction

● The term computer is derived from the word compute.
● The word compute means calculate.
● A Computer is an electronic machine that accepts data from the user, processes the
data by performing calculations and operations on it, and generates the desired
output results.
● Computer performs both simple and complex operations, with speed and accuracy.

Input --------🡪 Process------🡪 Output

● The computer system consists of 4 parts.
1. Hardware: Mechanical parts that makeup the computer as a machine.
● Example: Keyboard, Monitor, Hard disk drive, Printer, Floppy disk
drive, Processor, etc….
2. Software:
● Set of instructions that tell the computer about the tasks to be performed.
● Program: Set of instructions, written in a language understood by the
computer, to perform a specific task.
● Software: Set of programs and documents.
3. Data: Isolated values or raw values.
4. Users:
● People who write computer programs or interact with the computer.
● Also called skinware, liveware, humanware, or peopleware.
● Examples: Programmers, Data entry operators, System analyst and
computer hardware engineers.

Characteristics of Computer

● Speed: The computer can process data very fast, at the rate of millions of instructions
per second. Eg., Calculation and generation of salary slip, weather forecasting, etc.,
● Accuracy: Provides a high degree of accuracy.
● Diligence: The computer does not get tired or fatigued. It can perform long and
complex calculations with the same speed and accuracy from the start till the end.

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● Storage Capability: Large volumes of data and information can be stored in the
computer and also retrieved whenever required.
● Versatility: At one moment you can use the computer to prepare a letter document and
in the next moment you may play music or print a document.


History of Computer

1. Calculating Machines: ABACUS
● First mechanical calculating device.
● Used for counting large numbers.
2. Napier’s Bones
● Mechanical device
● Used for multiplication in 1617 by John Napier.
3. Slide rule
● Developed by Edmund Gunter.
● Can perform addition, subtraction, multiplication and division.
● Used till late 1970’s
4. Pascal’s Adding and Subtraction Machine
● Developed by Blaise Pascal.
● Can perform addition and subtraction.
● Consist of wheel, gears, and cylinders.
5. Leibniz’s Multiplication and Division Machine
● Developed by Gottfried Leibniz in 1673.
● Can perform multiplication and division.
6. Punch card system
● Developed by Jacquard to control the power loom in 1801.
● He invented a punched card reader, which recognizes the presence of hole in the
punch card as binary one and the absence of hole as binary zero.
7. Babbage’s Analytical Engine
● Developed by Charles Babbage in 1823.
● Charles Babbage is called as father of computer.
● Used to do complex mathematical calculations.
● Charles Babbage and Lady Ada Lovelace developed a general-purpose calculating
machine called analytical engine.
8. Hollerith’s Punched card Tabulating Machine
● Developed by Herman Hollerith.
● The machine could read the information from a punched card and process it
electronically.
The first computer was developed in the year 1940.

Generations of Computer

⮚ The computer has evolved from a large-sized simple calculating machine to a smaller but
much more powerful machine.
⮚ There are five generations of computer.
⮚ They are discussed in terms of
o The technology used by them.(hardware and software)

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o Computing characteristics(speed)
o Physical Appearance.
o Applications


First Generation (1940 to 1956): Using Vacuum Tubes
1. Hardware Technology: The computers used
⮚ Vacuum tubes for circuitry
⮚ Magnetic drums for memory
⮚ Input- through punched cards & paper tapes.
⮚ Output- displayed as printouts.
2. Software Technology:
⮚ Instructions were written in machine language.
⮚ Machine language uses 0’s and 1’s for coding.
⮚ Computers can solve one problem at a time.
3. Computing Characteristics: Milliseconds
4. Physical Appearance: Large size and occupies one large room.
5. Applications: Scientific applications
6. Examples:
⮚ UNIVersal Automatic Computer(UNIVAC)
⮚ Electronic Numerical integrator & Calculator(ENIAC)
⮚ Electronic Discrete Variable Automatic Computer(EDVAC)
Disadvantages:
1. Generates lot of heat since it uses large number of vacuum tubes.
2. Consume more electricity.
3. Very expensive to operate.
4. Difficult to program.

Second Generation (1956 to 1963): Using Transistors
1. Hardware Technology: The computers
⮚ Used transistors for circuitry.
⮚ Become faster, smaller, cheaper, energy efficient and reliable.
⮚ Used magnetic core technology for primary memory.
⮚ Used magnetic tapes and magnetic disk for secondary memory.
⮚ Input – through punched cards.
⮚ Output – Printouts.
2. Software Technology:
⮚ Instructions were written in assembly language.
⮚ Assembly language uses mnemonics like ADD for addition and SUB for
subtraction.
⮚ High level programming languages like COBOL and FORTRAN were
developed.
3. Computing Characteristics: Microseconds
4. Physical Appearance: Smaller compared to first generation.
5. Applications: Scientific and Commercial
6. Examples: PDP-8, IBM 1401 and CDC 1604.

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