meljun cortes c++ chap2 c program controls structure

8/10/2019 MELJUN CORTES C++ Chap2 C Program Controls Structure

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Introducing ’s Program

ontrol Statements

C Programming Language

MELJUN CORTES



MELJUN CORTES



MELJUN CORTES MBA MPA BSCS

School of Computer I nformation 3

Ex. 1

Read two numbers to A and B. Increase 1 number to A and decrease 1 number to B.

START

A = A + 1

B = B - 1

END

A, B

READ A, B

#include <stdio.h>

void main() {

int a, b;

printf(“Input two numbers : ”);

scanf(“%d%d”, &a, &b);

}

a = a + 1;b = b - 1;

printf(“A’s value : %d\n”, a);

printf(“B’s value : %d\n”, b);





Ex. 2

Read two numbers to A and B. Swap A for B.

A B

A B

temp





1. Become familiar with the if

If statements C’s selection statements

Conditional statements

Logical data

true

false

C doesn’t have boolean datatype.

Use int, char datatype for logical data

if(expression) statement ;

Execute when expression is true

The result is true or false





if (10>9) printf(“true”);


Relational operator > : greater than

expression

statement

true

false


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if (9 < 5) printf(“this will not print”);


Relational operator < : less than





Example 1

#include <stdio.h>

int main(void) {

int answer;

printf(“What is 10 + 14 ? ”);

scanf(“%d”, &answer);

if(answer == 10+14)printf(“Right!”);

return 0;

}





Example 2 (feet– meters conversion program)





Exercises

Write a program that asks the user for an integer

and then tells the user if that number is even or odd.(Hint, use C’s modulus operator %.)




if…

else logic flow

2. Add the else




Example 2

2. Add the else




Exercises

2. Add the else

Write a program that requests two numbers and then

displays either their sum or product, depending on

what the user selects.

input two number : 28 5

select operator ( 1 : sum, 2 : product ) : 1

28 + 5 = 33




Exercises

2. Add the else

Write a program that requests two numbers and then

displays bigger number.

input two number : 28 5

28 > 5





Code block : { the statements }

3. Create blocks of code

One logical

unit

One logical

unit





If the user enters any positive number, thisfragment prints the message


scanf(“%d”, &num) ;

if(num > 0) {

printf(“This is ”) ;

printf(“an example of ”) ;

printf(“a code block.”) ;

}





Example 1






Example 2






Exercises


Write a program that either adds or subtracts two

integers. First, prompt the user to choose an operation;

then prompt for the two numbers and display the result.

select operator ( 1 : add, 2 : subtract ) : 1

input two number : 28 5 28 + 5 = 33





4. Use the for loop

Simple exampleThis program uses a for loop to print the

numbers 1 through 10 on the screen

#include<stdio.h>

int main(void){

int num;

for(num=1; num<11; num=num+1)

printf(“%d ”, num) ;

printf(“terminating”);

return 0;

} 1 2 3 4 5 6 7 8 9 10 terminating





4. Use the for loop

Example (A for loop can run negatively)

#include<stdio.h>

int main(void){

int num;

//this loop will not execute

for(num=20; num>0; num=num-1)

printf(“%d ”, num) ;

printf(“terminating”);

return 0;

}20 19 18 17 …… 3 2 1 terminating





4. Use the for loop

Example (increment or decrement by more than one) This program counts to 100 by fives.

#include<stdio.h>

int main(void){

int i;

for(i=0; i<101; i=i+5)

printf(“%d ”, i) ;

return 0;

}0 5 10 15 20 …… 90 95 100





4. Use the for loop

Example 1. (addition-drill)





4. Use the for loop

Exercises 1.

Create a program that prints the numbers from 1 to 100.

1 2 3 …… …… 8 9 10: : : :: : : :: : : :

91 92 93 …… …… 98 99 100





4. Use the for loop

Exercises 2.

Write a program that prints the numbers between 17 to

100 that can be evenly divided by 17.

34 51 68 85





4. Use the for loop

Exercises 3.

Write a program similar to the prime-number tester,

except that it displays all the factors of a number entered

By the user.

For example, if the user entered 8, it would respond with

2 and 4.

Enter a number : 8

8’s factor => 2 4

5 Substitute C’s increment and





5. Substitute C s increment anddecrement Operators

Increment operator (++) num = num +1; num++;

Using for loop

Decrement operator (--)

count = count -1; count--;

for(num=1; num<some_value; num=num+1) ……

for(num=1; num<some_value; num++) ……






Before the variable( ++num )

First : increment expression execute.

After : the incremented value of variable is used for

expression.

#include<stdio.h>int main(void){

int i, j;

i = 10;

j = ++i;

// this will print 11 11

printf(“i and j : %d %d\n”, i, j) ;

return 0;

}







Before the variable( num++ )

If max = 1

Result

max = 2, count = 20

Arrangement

count = 10 * ++max;

count = 10 * ++max;max = max + 1;

count = 10 * max;



5. Substitute C’s increment and






Example 2.







Exercises 1.

Change all appropriate assignment statements in this program

to increment or decrement statements.

#include <stdio.h>

int main(void) {int a, b;

a=1;

a = a + 1;

b = a;

b = b – 1;

printf(“%d %d”, a, b);

return 0;

}







Exercises 2.

Enter a number. Compute summation until the number

from 1.

enter a number : 10

sum of 1 ~ 10 : 55



6 Expand printf()’s capabilities





6. Expand printf() s capabilities

Backslash codes

Represent characters that cannot be entered from the keyboard,

and non-printing characters

Escape character







'\n' (newline character)

It translates it into a carriage return/linefeed combination.

• backslash codes are character constants.

char ch;

ch = '\t'; /* assign ch the tab character */






number square cube

===============================1 1 1

2 4 8

3 9 27

: : :10 100 1000


ExerciseUsing for loop (1~10)

7. Program with C’s relational





gand Logical operators

Relational operators Compare two values and return a true or false result based

upon that comparison.

Logical operators

Connect together true/false results.







Truth table (AND, OR, NOT)







Precedence of operators The relational and logical operators are both lower in

precedence than the arithmetic operators.

10 + count > a + 12 (10 + count) > (a + 12)

var > max || ! (max==100) && 0 <= item







Example 1.

if(count != 0) …… if(count)

The expression !count is true only if count is zero.

if(count == 0) …… if(!count)







Example 2. (the outcome of a relational or logical operation)





and Logical operators

Example 3. (exclusive-OR) Demonstrate the xor()

Skills Check



Skills Check

Page 66 ~ 67

meljun cortes c++ chap2 c program controls structure

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