Programming Languages Salihu Ibrahim Dasuki (PhD) CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Machine language is Numeric  Machine code or machine language is a set of instructions executed directly by a computer's central processing unit (CPU).  Each instruction performs a very specific task, such as a load, a jump, or an ALU operation on a unit of data in a CPU register or memory.  Every program directly executed by a CPU is made up of a series of such instructions

 An assembly language is a low-level programming language for a computer, or other programmable device, in which there is a very strong (generally one-to-one) correspondence between the language and the architecture's machine code instructions.

 Assembly language uses a mnemonic to represent each low- level machine instruction or operation.  Before it can be executed on a computer, it needs to be converted into machine language.  An assembler is a program that creates object code by translating combinations of mnemonics and syntax for operations and addressing modes into their numerical equivalents.

 A programming language such as C, FORTRAN, or Pascal that enables a programmer to write programs that are more or less independent of a particular type of computer.  Such languages are considered high-level because they are closer to human languages and further from machine languages.  To execute a high language, it must be converted into a machine language using a compiler.

 1 st Generation ◦ Machine Language  2 nd Generation ◦ Assembly Language  3 rd Generation ◦ High level language such as Java, Ruby

 Computer programming (often shortened to programming) is a process that leads from an original formulation of a computing problem to executable computer programs.  To “program” is to construct a program that will execute on a computer.  A program is a collection of statement of 3 types: ◦ Declarative: e.g. names used to reference data ◦ Imperative: steps of the algorithm ◦ Comments: help explain the program

 Variables and data types  Assignment and statements  Control structures  Comments  Procedures  Functions

 Variable (computer science), a symbolic name associated with a value and whose associated value may be changed.  Variable types include int, float, double, char etc  Int age=45;

 The steps of the algorithm are described in the programming language using imperative statements.  One form of these is the assignment statement.

 The steps of the algorithm are described in the programming language using imperative statements.  One form of these is the assignment statement.

 They alter the execution path through the program. There are three types:

 Comments can be incorporated within a program.  They are means of explaining to someone reading or modifying the program what they program is all about.  Comments need to be meaningful.

 Comments can be incorporated within a program.  They are means of explaining to someone reading or modifying the program what they program is all about.  Comments need to be meaningful.

 Procedures are a means of organizing program codes into units that can be reused  Procedures do things, functions later returns things Int calc (int x, int y) Int sum=x + y; } Return sum;

 Procedures are a means of organizing program codes into units that can be reused  Procedures do things, functions later returns things Int calc (int x, int y) Int sum=x + y; } Return sum;