1. Control Structure in C.pdf
- 2. Introduction In C, statements are executed sequentially. C provides two styles of flow control to change the sequential execution of program: Branching (Decision Making) Looping Branching is deciding what actions to take and looping is deciding how many times to take a certain action.
- 3. 3 C language provides such decision making capabilities by supporting “IF” statement. Types of “IF” statements. Simple if statement if...else statement Nested if...else statement else if ladder Decision Making Sataement
- 4. 4 Used to execute or skip one statement or group of statements for a particular condition. Syntax: if (condition) { Block of statements; } Next Statement X; To execute only one statement, opening and closing braces are not required. If the condition is true then the statement or block of statements Gets executed otherwise these statements are skipped and Statement X will be executed Simple If
- 6. Example: #include<stdio.h> void main() { int i = 5; if (i >1) { printf(" i is greater than 1n"); } printf(" End of programn"); } Output:- i is greater than 1 End of Program 6
- 7. 7 The if....else statement is an extension of the simple if statement. Syntax: if (condition) { Block of statements-1; } else { Block of statements-2; } Next Statement; Simple If else Statement
- 9. 9 Example: #include<stdio.h> void main() { int i = 5; if (i >0) { printf (" i is greater than 0n"); } else { printf (" i is not grater than 0n"); } } Output:- i is greater than 0
- 10. 10 When a series of decisions are involved, we may have to use more than one if.....else statement in nested form. Syntax: if(condition-p) { if(condition-q) { statement-1; } else { statement-2; } statement-3; } else { statement-4; } NESTED IF-ELSE… STATEMENT
- 12. 12 Example:- #include <stdio.h> void main() { int a,b,c,big; a=4; B=6; C=3; If (a>b) { if (a>c) big=a; else big=c; } else { if (b>c) big=b; else big=c; } printf (“Largest no=%d”,big); } Output:- Largest no=6
- 13. 13 When a series of many conditions have to be checked we may use the ladder else if statement The structure of else-if ladder looks like a ladder Syntax: If (condition 1) statement-1; else if (condition 2) statement-2; else if (condition n) statement-n; else default statement; next statement; ELSE-IF…LADDER
- 14. Conditio n-1 Conditio n-2 Conditio n-n Statement- 1 Statement- 2 Statement- 3 Default statement T T T F F F Next Statement The conditions are evaluated from the top of the ladder to downwards. As soon on the true condition is found, the statement associated with it is executed and the control is transferred to the next statement – x (skipping the rest of the ladder.) When all the condition becomes false, the final else containing the default statement will be executed. 14
- 15. 15 Example: void main() { int i=2; if (i==0) printf ("i==0n"); else if (i==1) printf("i==1n"); else if (i==2) printf("i==2n"); else printf(“enter the value between 0 to 2n"); } Output : i==2
- 16. 16 Syntax: switch(expression) { case value1: block1; break; case value2: block2; break; ...... ..... default: default block; break; } next statement; Switch Statment
- 17. Switch (expressio n) Next Statement Default Block Block-4 Block-3 Block-2 Block-1 Value 1 Value 2 Value 3 Value 4 Default 17
- 18. 18 C has a built-in multiway decision statement known as a switch. The switch statement tests the value of a given variable (or expression) against a list of case values and when a match is found, a block of statements associated with that case is executed. The expression is an integer expression or characters. value1, value2, .... are constants or constant expressions and are known as case labels. block1, block2,...... are statement lists and may contain zero or more statements. Note that case labels end with a colon (:). The break statement at the end of each block signals the end of a particular case and causes an exit from the switch statement, transferring the control to the statement-n following the switch. The default is an optional case. When present, it will be executed if the expression does not match any of the case values. If not present, no action takes place if all matches fail and the control goes to the statement-n.
- 19. #include <stdio.h> int main() { int color = 1; printf("Please choose a color(1: red,2: green,3: blue):n"); scanf("%d", &color); switch (color) { case 1: printf("you chose red colorn"); break; case 2: printf("you chose green colorn"); break; case 3: printf("you chose blue colorn"); break; default: printf("you did not choose any colorn"); } return 0; }
- 20. 20 Example: void main() { int i,n = 5; for(i = 1; i<n; i= i+1) { switch(i%2) { case 0 : printf("the number %d is even n",i); break; case 1 : printf("the number %d is odd n",i); break; } } Output : the number 1 is odd the number 2 is even the number 3 is odd the number 4 is even
- 21. No. The if…else The switch-case 1. Is a two-way branching. Is a multi-way branching. 2. The nested if…else is complicated. Is easier to write. 3. The nested else…if can take many levels and it becomes difficult to match the else part to its corresponding if. No such problem occurs in switch- case. 4. Debugging becomes difficult. Tracing of errors and debugging is easy. 5. The test expression can be constant value or may involve any type of operator. Only constant integer expressions and characters values are allowed.
- 22. 22 C ?: operator is sometimes called conditional operator or ternary operator. Syntax: condition ? expression 1 : expression 2 C first evaluates the condition. If the condition is evaluated to true , expresion 1 is evaluated. Then the operator return the value of the expression 1. If the condtion is evaluated to false, expression 2 is evaluated. The value of the expression 2 is returned. The ?: Operator (Ternary operator)
- 23. 23 Example: void main() { int a=10,b=5,big; big=if(a>b)?a:b; printf(“The number %d is greater number n",big); } Output:- The number 10 is greater number
- 24. 24 The goto statement is a jump statement which jumps from one point to another point within a function. Used to transfer the program control unconditionally from one statement to another statement. Syntax : goto label; ………… ………… label: statement; or label: statement; ....... ....... goto label; Go to Statement:
- 25. 25 Example: void main() { int n = 0; Loop: printf ("n%d", n); n++; if (n<10) { goto Loop; } getch(); } Output : 0 1 2 3 4 5 6 7 8 9