Programming Languages, Lecture notes of Information Technology

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Class:FE-Chemical

Lecture # 1 (b)

Topic : Introduction To

Programming languages

 What is a Program A program is a list of instructions that the computer must follow in order to process data into information  What is Instruction An Instruction consist of statements used in a programming language  What is Programming It is a multistep process for creating that list of instructions

Types of Programming Languages  Low Level Computer Languages or Machine Language  Assembly Language  High Level Computer Languages

Cont…Types of Programming Languages

 Key Features of Low Levels Computer Languages

 This kind of Programming is considered fast  To program in machine language requires high knowledge of the CPU and machine instruction set This also meant high hardware dependency and lack of portability  Assembly or machine code could not run on different machines as they have a unique instruction set for each type of computer

Cont… Types of Programming Languages

 Assembly Languages

 Lying between low level languages and high level languages  Similar to low level/machine languages but much easier to program in because they allows user to substitute names for numbers

Cont… Types of Programming Languages

 Features of High Level Computer Languages

 Machine Independent  The comparative ease of use and learning, improved portability and simplified debugging , modifications led to the reliability and lower software costs

Generations of Programming Languages  First Generation Languages  Second Generation Languages  Third Generation Languages  Fourth Generation Languages  Fifth Generation Languages

Second Generation Languages

 Assembly languages

 Symbolic operation codes replaced binary operation codes.  Assembly language programs needed to be “assembled” for execution by the computer. Each assembly language instruction is translated into one machine language instruction.  Very efficient code and easier to write.

Third Generation Languages

 Closer to English but included simple

mathematical notation

 Programs written in source code which must be translated into machine language programs called object code  The translation of source code to object code is accomplished by a machine language system program called a compiler and an interpreter

Fifth Generation Languages  Fifth generation (programming) language ( 5 GL) is a grouping of programming languages build on the premise that a problem can be solved, and an application built to solve it, by providing constraints to the program (constraint-based programming), rather than specifying algorithmically how the problem is to be solved (imperative programming).

 Examples: Lisp, Scheme, SML

Compilation & Interpretation

 Two ways to convert a program into

machine language

 Compile the program

Translate the program before executing any instruction

 Interpret the program

Translate and execute a single instruction or a group of instructions