1 introduction to c program

Structure of C program Preprocessor directives Global variables Main(void) { Local variables Statements …..……… ……………. Return 0; } Function() { Local variables Statements ………….. } #include<stdio.h> #define num 10 Static Int I; //static or extern Main() { Int I, num; /* static, global, auto or registers declaration*/ Int a=5; // initialization Scanf(“%d”,&i); Printf(“i=%d,num=%d,a=%d”,I,num,a); }

Compilation and execution of c program Pre-processor Compiler Assembler Linker Source code Expanded code Assembly code Object code Executable code .c C code .i intermediate code .s assembly code .o object code .exe / a.out

Errors in c program Compile time error Run time error Pre processor error Translator error Linker error Segmentation error Bus error ……. …….. ...…….64 types of errors

Data types  Character data type (char)  Signed - 1 byte (-128 to 127)  Unsigned - 1 byte (0 to 255)  Integer data type (int)  Short int : signed - 1 byte (-128 to 127) Unsigned - 1 byte (0 to 255)  int : signed - 2 byte (-2G to 2G) Unsigned - 2 byte (0 to 4G)  long int : signed - 4 byte (-4G to 4G) Unsigned - 4 byte (0 to 8G)  Real data type (float and double)  Float - 4bytes (3.4e-38 to 3.4e+38)  Double - 8 bytes (1.7e-308 to 1.7e+308)  Long double - 10 bytes (3.4e-4932 to 3.4e+4932)  String data type (string) ‘a’ , ’1’ 123 , 0X1223 Float (0.25f) and double (0.25) “1234”, “nishma”

Operators • Arithmetic operator ( + , - , * , / , % ) – binary – doesn’t change the value – result (value) • Relational operator ( > , >= , < , <= , == , != ) – binary – doesn’t change the value – result (0 or 1) • Logical or Boolean operator (&& , || , ! ) – binary – doesn’t change the value – result (0 or 1) • Conditional operator ( [? :] ) – ternary – doesn’t change the value – result (true stat or false stat) • Bitwise operator ( & , | , ~ , << , >> ,^ ) – binary – changes the value • Increment and decrement operator ( ++ , -- ) – unary – changes the value • Size of operator ( sizeof() ) –unary –doesn’t change the value

Control statements Iterative Non - iterative Conditional Unconditional  For  While  Do while  If  Else if  Switch - case  Goto  Break  Return  Continue

If statement If (condition) { Statement1; Statement2; Statement3; } If (condition) Statement1; Statement2; Statement3; If (condition); { Statement1; Statement2; Statement3; } true

Example #include<stdio.h> Main() { Int a=10,b=20; If (a<b) { a=b; Printf(“greater=%d”,a); } } #include<stdio.h> Main() { Int a=10,b=20; If (a<b) a=b; Printf(“greater=%d”,a); }

If esle statement If (condition) Statement 1; Else Statement 2; If (condition) { Statement 1; } Else { Statement 2; } If (condition) { Statement 1; } Else Statement 2; If (condition) Statement 1; Else { Statement 2; } Condition Statement 1 Statement 2 Next statement True False

Example #include<stdio.h> Main() { Int a=10,b=20; If (a<b) { a=b; Printf(“greater=%d”,a); } else Printf(“greater=%d”,a); } #include<stdio.h> Main() { Int a=10,b=20; If (a<b) a=b; Printf(“greater=%d”,a); else Printf(“greater=%d”,a); }

Else if ladder If (expression 1) Statement 1; Else if (expression 2) Statement 2; Else if (expression 3) Statement 3; Else Statement 4; Nested if else ladder If (exp 1) { If (exp 2) { if (exp 3) { S1; } else S2; } else S3; } Else S4;

Switch case statement Switch (expression) { Case label 1 : S1; S2; break; Case label 2 : S1; S2; break; Default : S1; Result should be in Char, short int, int. Strings and float are not allowed Not mandatory

Example #include<stdio.h> Main() { Int a; Scanf(“%d”,&a); Switch (a) { Case 1 : printf(“%d”,a++); break; Case 2 : printf(“%d”,++a); break; Default:printf(“%d”,--a);

For statement For (exp 1 ; exp 2 ; exp 3) { Statement 1; Statement 2; } Initialization Condition checking Control variable operators Body of the loop For (exp 1 ; exp 2 ; exp 3); { Statement 1; Statement 2; }

Example For (i=0 ; i<=10 ; i++) { Printf(“%d”,i); } For (i=0 ; i<=10 ; i++); { Printf(“%d”,i); } o/p: 0 1 2 3 4 5 6 7 8 9 10 o/p: i=11

Nesting For statement For (exp 1 ; exp 2 ; exp 3) { Statement 1; Statement 2; for (exp 4 ; exp 5 ; exp 6) { statement 3; statement 4; } } Outer loop control variables and inner loop control variables will not be the same 1 2 3 8 4 5 6 7 For (i=0 ; i<4 ; i++) { n=i; for (j=0 ; j<n ; j++) { printf(“ %d ”,j); } printf(“n”); } o/p: i=0 , i<4 , n=0 ; j=0 , j<0; i=1 , i<4 , n=1 ; j=0 , j<1; j=1 , j<1; i=2 , i<4 , n=2 ; j=0 , j<2; j=1 , j<2;j=2 , j<2 i=3 , i<4 , n=1 ; j=0 , j<3; j=1 , j<3;j=2 , j<3; j=3 , j<3 i=4 , i<4 0 0 1 0 1 2

While statement While (expression) { Statement 1; Statement 2; } Expression Body of the loop True False Next statements While (exp1 ; exp2 ; exp3) { Statement 1; Statement 2; } Last exp (exp3) decides whether to enter the loop or not While (expression) Statement 1;

Example Int i=0; While (i==0) { Printf(“i=%dn”, i++); Printf(“i=%dn”,++i); } o/p: i=0 i=2 Int i=0; While (i==0); { Printf(“i=%dn”, i++); Printf(“i=%dn”,++i); } o/p: Infinite loop Doesn’t print any value

Do While statement Do { Statement 1; Statement 2; } While (expression); Expression Body of the loop True False Next statements Do Statement 1; While (expression);

Example Int i=0; Do { Printf(“i=%dn”, i++); Printf(“i=%dn”,++i); } While(i<10); o/p: i=0 , i=2 i<10 , i=2 , i=4 ………… i<10 , i=8 , i=10 i<10 next statement

Goto statement Forward jump Goto label; Statements; ………… …………… Label: Statements; ………… …………… Backward jump Label: Statements; ………… …………… Goto label; Statements; ………… …………… Example Int a; Start: Printf(“enter the valuen”); Scanf(“%d”,&a); Printf(“%d”,++a); Goto start;

Arrays Data_type array_name [index]; No of elements in the array To scan For (i=0 ; a[i] ; i++) { Scanf(“%d”,&a[i]); } To print For (i=0 ; a[i] ; i++) { printf(“%d”,a[i]); } Array representation A[i]=i[a]=*(a+i) Example: Int a[6]; Int a[6] = {10,20,30,40,50,60}; 1D array

2D array To scan For (i=0 ; i<n ; i++) { for(j=0 ; j<m ; j++) Scanf(“%d”,&a[i]); } To print For (i=0 ; a[i] ; i++) { for(j=0 ; j<m ; j++) printf(“%d”,a[i]); }

Strings Data_type string_name [index]; Example: char s[6]; char s[6] = “hello”; No of elements in the string To scan For (i=0 ; s[i] ; i++) { Scanf(“%c”,&s[i]); } Or Scanf(“%s”,s); To print For (i=0 ; s[i] ; i++) { printf(“%c”,s[i]); } Or Printf(“%s”,s); It is a collection of characters terminated by a null symbol (‘o’)

Functions Library function User defined function Example: Sqrt(); Function declaration Function call Function definition Return_type fun_name (type1 par1, type2 par2,…..); Fun_name (arg1, arg2, arg3); Return_type fun_name (parameter declarations) Return (exp);

Storage classes Auto Static Extern Register Default Garbage 0 0 Garbage Memory Stack frame Data segment Data segment Stack frame Scope locally Accessed directly within a fun or block Accessed within a fun Accessed within a fun Accessed directly within a fun or block globally Cannot be declared globally can access throughout the file. can access throughout the file. Cannot be declared globally Life Start When fun stack frame created When program is loaded into RAM Same as static When fun execution starts End When it gets deallocated When execution is completed Same as static When execution ends

1 introduction to c program

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1 introduction to c program