Introduction to c programming

Introduction to C programming

1. INTRODUCTION TO C PROGRAMMING

2. Program Program is a collection of instructions that will perform some task. Source code of a Hello World program written in the C programming language #include <stdio.h> int main(void) { printf("Hello world!\n"); return 0; }

3. INTRODUCTION TO C C was developed by Dennis Ritchie at Bell laboratory in 1972 It is an upgraded version of languages B and BCPL.

4. Features of C It is a structured programming language. It is highly portable. It is a middle level language. It is a case sensitive language. It uses Top-Down approach. It is a Free form language.etc,.

5. Structure of C program GLOBAL DECLARATION SECTION DOCUMENTATION SECTION PREPROCESSOR SECTION DEFINITION SECTION main() { Declaration part; Executable Part; } sub program section { Body of the subprogram; }

6. Executing a C Program Enter the program in a C editor. Save the program (File  Save) or F2. Use the extension .c for saving the file. Eg: sample .c Compile the program(Compile  Compile) or Alt+F9. Run the program(Run  Run) or Ctrl+F9.

7. Executing C program using UNIX Enter the program in vi editor. Save the file using :wq Use the extension .c for saving the file. Eg: sample .c Compile the program. Eg: cc sample.c (or) gcc sample.c Run the program using a.out .

8. Identifiers Identifiers are names given to various program elements such as functions and arrays etc,. Example: int total,marks; Here total and marks are user defined identifiers.

9. Rules for naming identifier First character must be alphabetic or underscore. Must consist only of alphabetic characters, digits, or underscores. Only the first 31 characters of an identifier are significant and are recognized by the compiler. Cannot use a keywords or reserved word (e.g. main, include, printf & scanf etc.). No space are allowed between the identifiers etc,. C is case sensitive, e.g. My_name  my_name .

10. Examples of Valid and Invalid Names Variables : Variable is an identifier that is used to represent some specified type of information. Eg: x=3 Here x is variable.

11. Keywords auto register continue double typedef for int char signed struct extern void break return default else union goto long const sizeof switch float do case short if enum unsigned static while It is a reserved word, which cannot be used for anything else. Examples:

12. Constants Constants Character Constants Numeric Constants Real Constant Integer Constant String Constant Single Character Constant Constants Numeric Constants Integer Constant Constants Numeric Constants Real Constant Integer Constant Constants Numeric Constants Single Character Constant Real Constant Integer Constant Constants Numeric Constants String Constant Single Character Constant Real Constant Integer Constant Constants Numeric Constants Constants Numeric Constants Character Constants Numeric Constants It is an entity whose value does not changes during the execution.

13. Numeric constants Integer constants It is formed using a sequence of digits. Decimal - 0 to 9 . Octal - 0 to 7. Hexa - 0 to 9 ,A to F Eg: 10,75 etc. Rules for defining Integer Constant: It must have at least one digit. Decimal point are not allowed. No blank space or commas are allowed. It can be either positive or negative. Etc,.

14. Numeric constants (Cont) Real constants It is formed using a sequence of digits but it contain decimal point. length, height, price distance measured in real number. Eg: 2.5, 5.11, etc.

15. Character constants Single character constant A character constant is a single character they also represented with single digit or a single special symbol which is enclosed in single quotes. Eg : ‘a’, ‘8’,’_’etc. String constants String constant are sequence of characters enclosed with in double quote. Eg : “Hello” ,”444”,”a” etc,.

16. Data Types A data type is a classification identifying one of various types of data, such as real-valued, integer or Boolean, that determines the possible values for that type

17. Integer A number without a fraction part : integral number. Integer occupies 2 Bytes . The Control or Format String for integer is %d . C supports three different sizes of the integer data type : short int int long int

18. Floating Point A floating-point type is a number with a fractional part, e.g. 56.78. Floating point numbers occupies 4 Bytes. The Control or Format String for float is %f. C supports three different sizes of the float data type Double float long double

19. Character Character are generally stored using 8 bits(1 Byte) of the internal storage. The Control or Format String for Character is %c . Character ASCII code value a 97(decimal) or 01100001(binary) x 120(decimal) or 01111000(binary)

20. Void The void type has no values and no operations. Both the set of values and the set of operations are empty.

21. Entire Data types in c: Data type Size(bytes) Range Format string (or)Control String Char 1 128 to 127 %c Unsigned char 1 0 to 255 %c Short or int 2 -32,768 to 32,767 %i or %d Unsigned int 2 0 to 65535 %u Long 4 -2147483648 to 2147483647 %ld Unsigned long 4 0 to 4294967295 %lu Float 4 3.4 e-38 to 3.4 e+38 %f or %g Double 8 1.7 e-308 to 1.7 e+308 %lf Long Double 10 3.4 e-4932 to 1.1 e+4932 %lf

22. Variable ’ s Declaration To create a variable, you must specify the type. Example: float price; int a,b ; char code;