Computer blog

C is a general-purpose, imperative computerprogramming language, supporting structured programming, lexical variable scope and recursion, while a static type system prevents many unintended operations

What is program?

—  A computer program is a sequence of instructions written using a Computer Programming Language to perform a specified task.

—  The two important terms that we have used in the above definition are −

¡  Sequence of instructions

¡  Computer Programming Language

—  To understand these terms, consider a situation when someone asks you about how to go to a nearby KFC. What exactly do you do to tell him the way to go to KFC?

—  You will use Human Language to tell the way to go to KFC, something as follows −

¡  First go straight, after half kilometer, take left from the red light and then drive around one kilometer and you will find KFC at the right.

—  Now, try to map the situation with a computer program.

—  The above sequence of instructions is actually a Human Program written in English Language, which instructs on how to reach KFC from a given starting point.

—  In case of computer programming we will write instructions in a programming language to do a particular task by the computer.

—  A computer program can range from 2 lines to million lines of instructions.

—  A computer without a computer program is just a dump box; It is programs that make computers active.

—  Commonly used programming languages are.

¡  C,C++,Java,C#,Php,Python,Ruby,Perl etc.

Algorithm

—  Algorithm is a set of instruction used to solve a particular problem in a generic logical language usually in the form of pseudocode.

Program

—  Program is basically the implementation of that instructions in a programming language to do a particular task or to solve a problem.

—  A typical programming task can be divided into two phases:

—  Problem solving phase

¡  produce an ordered sequence of steps that describe solution of problem

¡  this sequence of steps is called an algorithm

—  Implementation phase

¡  implement the program in some programming language

—  First produce a general algorithm (one can use pseudo code)

—  Refine the algorithm successively to get step by step detailed algorithm that is very close to a computer language.

Pseudo code

—  Pseudo code is an artificial and informal language that helps programmers develop algorithms. Pseudo code is very similar to everyday english.

—  Example: Write an algorithm to determine a student’s final grade and indicate whether it is passing or failing. The final grade is calculated as the average of four subjects marks.

Pseudo code:

—  Input a set of 4 marks

—  Calculate their average by summing and dividing by 4

—  if average is below 50

                                Print “FAIL”

                else

                                Print “PASS”

Algorithm:

                Step 1:                  Input M1,M2,M3,M4

    Step 2:              GRADE ¬ (M1+M2+M3+M4)/4

    Step 3:              if (GRADE < 50) then

                                                                Print “FAIL”

                                                                else

                                                                                Print “PASS”

                                                                endif

High level languages

—  A high-level language is a programming language such as C++,Java or Pascal that enables a programmer to write programs that are more close to human languages.

—   Such languages are not directly understood by the computer and are translated into machiene language with the help of compilers and interpreters.

Mid level languages

—  Mid level languages acts as an intermediate language b/w high and low level languages.

—  It is called mid level because it is close to machiene as well as high level languages.

C is a kind of a mid level language.Programmer use it to do system programming for writing operating system as well as application programming.

Low level languages

—  A low-level language is a programming language that deals with a computer’s hardware components and are machine oriented.

—  These languages are directly understood by the computer because they are in the form of 0’s and 1’s.

—  Examples of low-level languages are assembly and machine languages.

— 
It is also called machine language or binary language.

—   

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	Instructor: Fahad  Zia