Tutorial ICS431 – Introduction to C
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Tutorial
ICS431 – Introduction to C
Example ( 1 )
int main(){
float radius, area;
printf(“Enter the radius : “);scanf(“%f”, &radius);area = radius * radius * 3.1415;printf(“area = %f\n”, area);
return 0;}
Formatting Specifier
(ٍSpecifierFormat
%fFloat
%d or %iInteger
%ldLong integer
%lfDouble
%cChar
%sString
%pAddress
Again: Example ( 1 )
#define PI 3.14159
int main(){
float radius, area;
printf(“Enter the radius : “);scanf(“%f”, &radius);area = radius * radius * PI;printf(“area = %f\n”, area);
return 0;}
Example ( 2 )
int main(){
int std_id;float grade;
printf(“Enter student ID: “); scanf(“%d”, &std_id);printf(“Enter his grade: “); scanf(“%f”, &grade);printf(“Student %d got “, std_id);if (grade >= 95.0) printf(“A+\n”);else if (grade >= 85.0) printf(“A\n”);else if (grade >= 75.0) printf(“B+\n”);else if (grade >= 70.0) printf(“B\n”);else if (grade >= 65.0) printf(“C\n”);else if (grade >= 60.0) printf(“D+\n”);else if (grade >= 50.0) printf(“D\n”);else printf(“F\n”);
}
Exercise ( 1 )
Write C code to solve the quadratic equation ax^2 + bx + c = 0.
- Consider only the real solutions.
- Check the input’s validity
- Make you program friendly interface.
- Square root function is sqrt().
Solution ( 1 )
int main(){
float a, b, c;float d, x1, x2;
printf(“Enter the coefficient of x^2: “); scanf(“%f”, &a);printf(“Enter the coefficient of x: “); scanf(“%f”, &b);printf(“Enter the constant value: “); scanf(“%f”, &c);
if (a == 0 && b == 0)printf(“Invalid data: no equation\n”);
else if (a == 0) {
x1 = -c / b;printf(“First order equation. x = %.2f\n”, x1);
}
Solution ( 1 )
else {d = b*b – 4*a*c;if (d < 0)
printf(“No real solution\n”);else if (d == 0) {
x1 = -b / (2*a);printf(“Single solution. x = %.2f\n”, x1);
}else {
x1 = (-b + sqrt(d)) / (2*a);x2 = (-b – sqrt(d)) / (2*a);printf(“ x[1] = %.2f\n”, x1);printf(“ x[2] = %.2f\n”, x2);
}}return 0;
}
Example ( 3 )
int main(){
int month;
printf(“Month number: “); scanf(“%d”, &month);printf(“Number of days is “);switch (month) {
case 1: case 3: case 5: case 7:case 8: case 10: case 12: printf(“31\n”);break;case 4: case 6: case 9: case 11: printf(“30\n”);break;case 2: printf(“28 or 29\n”); break;default: printf(“\nInvalid number\n”);
}return 0;
}
Example ( 4 )
int main(){
int number;int i;
printf(“Enter an integer number: “); scanf(“%d”, &number);printf(“The positive divisor(s) of %d is(are): “);for (i=2; i<number/2; i++)
if (number % i == 0) printf(“%d”, i);
return 0;}
Boolean type
C does not support boolean data type.
- However, boolean variables (in C) are integer variables.
- ZERO value means FALSE.
- NON-ZERO value means TRUE.
Exercise ( 2 )
Write a C code to determine if a given number is prime or not.
- You can use break or continue within the loop body.
Solution ( 2 )
int main(){
int number, i;int is_prime = 1; /* boolean variable */
printf(“Enter a number: “); scanf(“%d”, &number);for (i=2; i<number/2; i++)
if (number % i == 0) {is_prime = 0;break;
}if (is_prime)
printf(“%d is a prime number\n”, number);else
printf(“%d is not a prime number\n”, number);return 0;
}
Example ( 4 )
int is_prime (int number){
int flag = 1, i;
for (i=2; i<number/2; i++)if (number % i == 0) {
flag = 0;break;
}return flag;
}
int main(){
int number;
printf(“Enter a number: “); scanf(“%d”, &number);if (is_prime(number))
printf(“%d is a prime number\n”);else
printf(“%d is not a prime number\n”);return 0;
}
Declare before Use
Example ( 5a )
int main(){
int number;
printf(“Enter a number: “); scanf(“%d”, &number);if (is_prime(number))
printf(“%d is a prime number\n”);else
printf(“%d is not a prime number\n”);return 0;
}
int is_prime (int number){
int flag = 1, i;
for (i=2; i<number/2; i++)if (number % i == 0) {
flag = 0;break;
}return flag;
}
Example ( 5b )
#include <stdio.h>
int is_prime (int);
int main(){
int number;
printf(“Enter a number: “); scanf(“%d”, &number);if (is_prime(number))
printf(“%d is a prime number\n”);else
printf(“%d is not a prime number\n”);return 0;
}
int is_prime (int number){
int flag = 1, i;
for (i=2; i<number/2; i++)if (number % i == 0) {
flag = 0;break;
}return flag;
}
Global vs Local
• SCOPE
• LIFE TIME
• LINKAGE
SCOPE
• Variable declared outside any function has global scope. Global variable
• Variable declared inside a function has local scope (within the function body). local variable
• Global variable with static modifier has scope within the file only.
LIFE TIME
• Global variable has global life-time
• Local variable has local life-time
• Local variable with static modifier has global life-time.
LINKAGE
• Internal linkage
• External linkage
Files
• SCOPE
• LIFE TIME
• LINKAGE
Standard files
• Any C program has THREE standard files– stdin (refer to keyboard)– stdout (refer to terminal window)– stderr (refer to terminal window)
• These files are declared in stdio.h
• fprintf() is used to print to a file
• fscanf() is used to read from a file
Standard files
• printf(“Area = %d\n”, area);
• fprintf(stdout, “Area = %d\n”, area);
• scanf(“%f”, &radius);
• fscanf(stdin, “%f”, &radius);
User files
FILE *myfile;
myfile = fopen(“data.dat”, “w”);
printf(myfile, “Hello world!\n”);
Integer Representation
• Integer values can be represented:– As decimal.
12 100 188– As octal.
014 0144 0274– As hexadecimal.
0xC 0x64 0xbc
char
• The data type char means 1-byte integer.
• Characters are represented as 1-byte.
unsigned modifier
• unsigned char
• unsigned int OR unsigned
• unsigned long
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