INTRODUCTION TO C

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INTRODUCTION TO C

INTRODUCTION


  • C is a general-purpose, high-level language that was originally developed by Dennis M. Ritchie to develop the UNIX operating system at Bell Labs.
  • C was originally first implemented on the DEC PDP-11 computer in 1972.
  • The UNIX operating system, the C compiler, and essentially all UNIX applications programs have been written in C.
  • The C has now become a widely used professional language for various reasons.

HISTORY OF C :

  1. C programming language was developed in 1972 by Dennis Ritchie at bell laboratories of AT&T (American Telephone & Telegraph), located in the U.S.A.
  2. Dennis Ritchie is known as the founder of the c language. It was developed to overcome the problems of previous languages such as B, BCPL, etc.
  3. Initially, C language was developed to be used in UNIX operating system. It inherits many features of previous languages such as B and BCPL.

FEATURES AND APPLICATION OF C :

  1. FEATURES :

    • Programs Written in C are efficient and fast. This is due to its variety of data type and powerful operators.
    • C is highly portable this means that programs once written can be run on another machines with little or no modification. Another important feature of C program, is its ability to extend itself.
    • A C program is basically a collection of functions that are supported by C library. We can also create our own function and add it to C library.
  2. APPLICATION :

    • C language was used for system development work, with the programs that make-up the operating system.
    • C was adopted as a system development language because it produces code that runs nearly as fast as code written in assembly language.

PROGRAM DEVELOPMENT LIFE CYCLE :

  1. REQUIREMENTS :

    1. In this phase we are defining the problem statement and also define the boundaries.

    2. We also decide our requirements and the output of the problem solution that we have defined.

  2. ANALYSIS :

    1. In this phase we determine and analyse the requirements to solve the problem.

    2. We also gather the required resources and determine the bounds of the solution.

  3. DESIGN :

    1. In this phase we actually design the program according to its requirements.

    2. Here we actually create a blue print for our program that how it should be.

  4. CODING :

    1. In this phase we uses a programming language to write actual programming instructions.

    2. We here construct actual program for development.

  5. TESTING :

    1. In this phase, we check whether the code written in previous step is solving the specified problem or not.

    2. We also test that whether it is providing the desired output or not.

  6. IMPLEMENTATION :

    1. In this phase, we implement the program we have created.

    2. After completing all the previous steps we actually implement our program live to the users.

  7. MAINTENANCE :

    1. In this phase, the program is actively used by the users.

    2. If the user encounters any problem or wants any enhancement,then we need to repeat all the phases from the starting, so that the encountered problem is solved or enhancement is added.


FLOWCHART SYMBOLS :

SYMBOL NAME FUNCTION
ARROW It is a type of connector which represents the relationship between the symbols.
START/STOP It represents the starting and ending point.
PROCESSING It represents the process to be done.
INPUT/OUTPUT It represents the input and output in a program.
DESCISION It indicates all the types of the decision statements.

DESIRABLE PROGRAM CHARACTERISTICS :

  1. INTEGRITY :

    1. This refers to the accuracy of the calculations.

    2. It should be clear that all the calculations must be carried out correctly.

    3. Thus, the integrity of the calculations is an absolute neccessary.

  2. CLARITY :

    1. It refers to the overall readability of a program.

    2. It should be possible for the other programmers and also for the original programmer to understand the program logic.

  3. SIMPLICITY :

    1. The clarity and accuracy of a program are usually enhanced by keeping things as simple as possible.

    2. A program should be simple to understand and also it should be user friendly.

  4. EFFICIENCY :

    1. It is concerned with the execution speed of a program and efficient memory utilization.

    2. These are the general important goals,though they should not be obtained by the expense of clarity or simplicity.

  5. MODULARITY :

    1. A program can be break down in sub-parts.

    2. In C such modules are called functions.

    3. It enhances the accuracy and clarity of a program.

  6. GENERALITY :

    1. A program should be kept general as possible, with reasonable limits.

    2. A considerable amount of generality can be obtained with very little programming effort.

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