Revision• Language generations• Two’s and One’s Complement and Sign

and Magnitude

Language Generations:

Evolution of Programming Languages

Lan

gu

age

Gen

era

tions

First Generation (1s and 0s)

Second Generation

(Mnemonics) Third Generation

(High-Level Language)

Fourth Generation (Drag

and Drop)Fifth Generation

(Artificial Intelligence)

First Generation The first generation of languages

was very difficult to understand and also to code

This language was based on machine code language, hence the programmer would need to use binary

For this particular generation, punched tape was used, where a hole would represent a 1 and no-hole meant a 0.

Second Generation / Assembly Language

The second generation language, was also based on machine code,

This language was much easier as it used mnemonics (short words)

Programming was much easier because the programmer did not have to remember a list of binary digits

Keywords are used in this language such as ADD, SUB, JMP, MUL, etc

Third Generation / High-level Language

The third generation of languages was a very big improvement from the second generation

This generation incorporated the use of English-like statements

Examples of 3GLs are C, C++, Pascal and JAVA.

Examples of the 3rd Generations FORTRAN - mathematics formulas, scientific

problems, engineering problems COBOL – business oriented BASIC – very easy to understand, ideal to learn

programming PASCAL – mostly used for teaching purposes C – used to write operating systems, database

management system, scientific applications LISP – artificial intelligence LOGO – teach children problem-solving and

programming skills C ++ - An improved C, very popular and powerful JAVA – Very popular and powerful, also cross-platform

Fourth Generation The fourth generation language is a is

much closer to the human language

A typical example of the ease of use of 4th generation languages is the creation of a GUI.

To create a GUI in JAVA would be quite difficult because of the code required for each component, with any 4GL creating an interface is a simple matter of drag and drop

This generation is used a lot with databases

Fifth Generation Lastly we have the fifth

generation languages, which are the closest to the human language

This generation is used in artificial intelligence

Number Systems:Two’s and One’s

Complement and Sign and Magnitude

ComplementationComplementation is used to represent

positive and negative numbers in binary

This system requires numbers to be represented by a fixed register size.

There are two forms of complementation, one’s complement and two’s complement.

Ones Complement One’s complement is used to represent

negative numbers

Lets say we have 4510

When using 8 bits 4510 = 001011012

If we change 4510 to -4510 The binary representation changes by converting 0s to 1s and 1s to 0s;

001011012 110100102. after ones complement

Examples

Decimal Unsigned Binary

One’s Complement

-10910 11011012 00100102

-22910 111001012 000110102

Decimal Unsigned Binary

One’s Complement

-8910 010110012 101001102

-6410 10000002 01111112

-8910

-6410

Two’s Complement Two’s complement allows us to

perform subtractions with binary numbers

With two’s complement we start converting 1s to 0s and 0s to 1s after the first 1

Lets take the previous example of -4510,

Decimal Unsigned Binary

Two’s complement

-4510 001011012 110100112

Examples

Decimal Binary Two’s Complement

-1010 000010102 111101102

-4210 001010102 110101102

-5510 001101112 110010012

-6010 001111002 110001002

-5510

-6010

Sign and MagnitudeWhen we have a fixed register we

might want to store our binary number in a certain way

The three ways are using;1. sign and magnitude (first digit is

0 = positive, first digit is1 = negative)

2. one’s complement 3. two’s complement.

Example Lets say I have an 8 bit register

and want to store -1410

The number changes since it is negative, we first change it to binary = 000011102

Sign and Magnitude 10001110 Note that the fist digit is 1 because in this

case 14 is a negative number.

One’s Complement 11110001 In this case we simply applied NOT on the

binary value of 14.

Two’s Complement 11110010 We change the binary number 14 into two’s complement

Example 2 Lets say I have an 8 bit register

and want to store 1410

The number does not change since it is a positive number, we first change it to binary = 000011102Sign and Magnitude 00001110 Note that the fist digit is 0 because in this

case 14 is a positive number.

One’s Complement 00001110 In this case we simply leave the binary number the same

Two’s Complement 00001110 In this case we simply leave the binary number the same