Repetition Statements

305171 Computer Programming RattapoomWaranusast Department of Electrical and Computer Engineering Faculty of Engineering, Naresuan University Repetition Statements

Control Structures Revisit • Control structures control the flow of execution in a program or function. • Instructions are organized into 3 kinds of control structures • Sequence • Selection (decision, condition) • Repetition (looping)

Sequence Structure • a series of actions are performed in sequence { int a,n; n = 7; printf("n = %d\n",n); printf("a = ++n\n"); a = ++n; printf("n = %d, a = %d\n",n,a); }

n = 13? n = n + 1 Decision Structure get n • One of two possible actions is taken, depending on a condition. No Yes display“Lucky You” : : scanf(“%d”, n); if (n == 13) { printf(“Lucky you!”); n++; } printf(“You entered %d.”,n); : : display“You entered”and n

YES x < y? A Repetition Structure • A repetition structure represents part of the program that repeats. This structure is commonly known as a loop. • In the flowchart segment, the question “is x < y?” is asked. If the answer is yes, then Process A is performed. The question “is x < y?” is asked again. Process A is repeated as long as x is less than y. When x is no longer less than y, the repetition stops and the structure is exited.

Conditions • A program choose among alternative statements by testing the value of key variables. • Most conditions that we use to perform comparisons will use relational operators. • With logical operators, we can form more complicated conditions or logical expressions.

Loops • Loops are used to repeat a block of code. • Being able to have your program repeatedly execute a block of code is one of the most basic but useful tasks in programming. • There are three types of loops: while, for, and do..while. Each of them has their specific uses.

While statement • while loops are very simple. The basic structure is while ( condition ) statement; • If the condition is true (non-zero), the statement will be executed until the condition is false (zero). • Multiple statements can be grouped by putting them inside curly braces {, }.

x < 10? x = x + 1 while statement x = 0 • Example : : int x = 0; while ( x < 10 ) { printf( "%d\n", x ); x++; } printf (“end\n”); : : No Yes displayx display“end”

While Statement • Exercise 1: Basic while • Start and prepare to run a new project in VC++ Express • Copy the code from while.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code.

While Statement • Exercise 2: Summation using while • Start and prepare to run a new project in VC++ Express • Copy the code from sumscore.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to compute mean of the score.

While Statement • Exercise 3: Summation using while 2 • Start and prepare to run a new project in VC++ Express • Copy the code from sumscore2.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to compute mean of the score.

While Statement • Exercise 4: Factorial • Start and prepare to run a new project in VC++ Express • Copy the code from factorial.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code.

While Statement • Exercise 5: Yes or No • Start and prepare to run a new project in VC++ Express • Copy the code from yesno1.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the original code to cover small letters.

While Statement • Exercise 6: Infinite loop • Start and prepare to run a new project in VC++ Express • Copy the code from infinite.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code so that it no longer an infinite loop.

Infinite Loops • Infinite loops are loops that never end. • They are created when a loop’s expression is never set to exit the loop. • Every programmer experiences an infinite loop at least once in his or her career.

do...while • The do-while loop is similar to the while loop except the relational test occurs at the bottom (rather than top) of the loop. • This ensures that the body of the loop executes at least once. • As long as the condition is True (non zero), the body of the loop continues to execute.

do...while • The format of the do-while is do statement; while ( condition ); • The condition must be enclosed within parentheses, just as it does with a while statement. • Notice the semi-colon at the end of while condition.

x = x + 1 x < 10? do...while statement x = 10 • Example : : int x = 10; do { printf( "%d\n", x ); x++; } while ( x < 10 ); printf (“end\n”); : : displayx No Yes display“end”

do...While Statement • Exercise 7: do...while • Start and prepare to run a new project in VC++ Express • Copy the code from dowhile.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code.

do...While Statement • Exercise 8: Yes or No 2 • Start and prepare to run a new project in VC++ Express • Copy the code from yesno2.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the original code to cover small letters.

do...While Statement • Exercise 9: Check for a negative number • Start and prepare to run a new project in VC++ Express • Copy the code from checknegative.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to check for positive value, even or odd number.

for statements • The for loop enables you to repeat sections of your program for a specific number of times. • Unlike the while and do-while loops, the for loop is a determinate loop. This means when you write your program you can usually determine how many times the loop takes place.

For Statements • The format of the for loop is for (start_expr; condition; count_expr) statement; • C evaluates the start expressionbefore the loop begins. Typically, the start expression is an assignment statement, but it can be any legal expression. C looks at and evaluates start expression only once, at the top of the loop. • Every time the body of the loop repeats, thecount expressionexecutes, usually incrementing or decrementing a variable. The conditionevaluates to True (nonzero) or False (zero), and then determines if the body of the loop repeats again.

for Statement • Exercise 10: for loop • Start and prepare to run a new project in VC++ Express • Copy the code from for.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to use other increment or initialization methods. • Modify the code to use only while loop.

for Statement • Exercise 11: Range • Start and prepare to run a new project in VC++ Express • Copy the code from range.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to count the number of integers between two inputs. • Modify the code to calculate the sum of all integers between A and B, and also find the average.

for Statement • Exercise 12: Even and odd revisit • Start and prepare to run a new project in VC++ Express • Copy the code from evenodd.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to let the user input the minimum and maximum numbers. • Modify the code to count the integers between A and B that are divisible by 5.

for Statement • Exercise 13: Factorial revisit • Start and prepare to run a new project in VC++ Express • Copy the code from factorial.c and paste into the code editor. • Modify the code to use only for loop.

while and for equivalence for (start_expr; condition; count_expr) statement; is equivalent to start_expr; while ( condition ) statement; count_expr;

Break statement • The break statement is used to manipulate program flow in structures such as loops. • When a break statement is executed in a loop, the loop is terminated and program control returns to the next statement following the end of the loop.

Break Statement • Exercise 14: break statement • Start and prepare to run a new project in VC++ Express • Copy the code from break.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to use while loop.

continue statement • The continue statement is used to manipulate program flow in a loop structure. • When executed, any remaining statements in the loop are passed over and the next iteration of the loop is sought.

Continue Statement • Exercise 15: continue statement • Start and prepare to run a new project in VC++ Express • Copy the code from continue.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to use while loop.

Nested loops • Any C statement can go inside the body of a loop—even another loop. When you put a loop within a loop, you are creating a nested loop. • Each time the outer loop is repeated, the inner loops are reentered, their loop control expressions are reevaluated, and all required iterations are performed.

Nested loops • Exercise 16: Nested loops • Start and prepare to run a new project in VC++ Express • Copy the code from nestedfor.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to print more than one rectangle.

j < row? i = i + 1 Nested Loops j = 0 • Example : : for(j = 0; j < row; j++) { for(i = 0; i < col; i++) { printf("*"); } printf("\n"); } : : No Yes j = j + 1 i = 0 i < col? No new line Yes display*

Nested loops • Exercise 17: Multiplication table • Start and prepare to run a new project in VC++ Express • Copy the code from mtable.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to allow a user to specify the first and the last tables.

Some common math Functions int abs (int x); IxIdouble fabs (double x); IxI double sin (double x); sin xdouble cos (double x); cos xdouble tan (double x); tan x double asin (double x); sin-1 x double acos (double x); cos-1 x double atan (double x); tan-1 x double exp (double x); exdouble log (double x); ln xdouble log10 (double x); log xdouble pow (double x,double y); xydouble sqrt(double x); x

Math function • Exercise 17: Multiplication table • Start and prepare to run a new project in VC++ Express • Copy the code from distance.c and paste into the code editor. • Run the code and observe the result. • Let’s play with the code. • Modify the code to compute an angle forms by the line that pass these points and x-axis.

Repetition Statements