Programming in C - 05 - Variables

8/17/2019 Programming in C - 05 - Variables

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Variable Types

Integer• int

Character• char

Floating Point• float

• double

C String• char*

• char[]

Boolean• bool






Variable Types

Variable Type Declaration

char char c = ‘a’;

int int n = 10;

Bool (Not Standard… More on this later…) bool b = false;

float float f = 10.22;

double double d = 10.1123456;char* char* ch = “Hey, Buddy!”;

char[]Requires string.h

char buffer[50];strcpy(buffer, “Hey, Buddy!”);






Variable Constraints: Signed Vs. Unsigned

Signed: # cpositive or n

Unsigned: #positi

Signed is typically default signed int n1 = -100;

Same as:

int n1 = -100;

unsigned int n2 = 122;




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Variable Constraints: Size Qualifiers

Specifies size requirements for Integers• In standard C integers are 16-bits… Although, default sizes of data type

are different between systems based on OS, system architecture, com

etc…

• C contains libraries that standardize this.. We will discuss this later!

Qualifier Description Declaration

short 16-bit integerUnsigned Range: [0 to 65,535]Signed Range: [-32,768 to 32,767]

short int n1 = 0;

short n2 = 0;

long 32-bit integerUnsigned Range: [0 to 4,294,967,295]

Signed Range: [-2,147,483,648 to 2,147,483,647]

long int n1 = 9999;

long n2 = 10000;

long long 64-bit integerUnsigned Range: [0 to 18,446,744,073,709,551,615]

Signed Range: [-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807]

long long int n1 =

long long n2 = 1000





Variable Constraints: Size Qualifiers

Can also be used with Signed or Unsigned

keywords

unsigned long int n = 1234567890;





Variable Constraints: Constants

Variable that retains its value throughout the

execution of a program (read only)

const float pi = 3.14;





Variable Constraints: Symbolic Constants

Constant variable that is declared as a

preprocessor directive






Constant variable that is declared as a

preprocessor directive






Can also be used to store portions of code






Typecasting

Converting one data type to another

int x = 4;

int y = 1;

float z = y / x;






Typecasting


int x = 4;

int y = 1;

float z = y / x;

T i






Typecasting


int x = 4;

int y = 1;

float z = (float)y / (float)x;

T ti






Typecasting


char ch = ‘A’;

int c = (int)ch;

T ti






Typecasting


char ch = ‘A’;

int c = (int)ch;

D t T C i






Data Type Conversion

Must include stdlib.h

ASCII to Integerint n = atoi(“123456”);

ASCII to Float

float f = atof(“123456.12”);

Data Type Conversion: sprintf







Converts any data type to a Cstring using a formatted

#include <stdio.h>

int main()

{

char ch[256];

int num = 12345;

sprintf(ch, "%d", num);

printf("%s\n", ch);

return 0;

}









#include <stdio.h>

int main()

{

char ch[256];

int num = 12345;


printf("%s\n", ch);

return 0;

}









#include <stdio.h>

int main()

{

char ch[256];

int num = 12345;


printf("%s\n", ch);

return 0;

}

12345

Gotcha!!!!






Gotcha!!!!

Pay attention to this…

#include <stdio.h>int main()

{

char c;

printf("%c\n", c);

return 0;

}

Gotcha!!!!






Gotcha!!!!



{

char c;

printf("%c\n", c);

return 0;

}

Gotcha!!!!






Gotcha!!!!



{

char c;

printf("%c\n", c);

return 0;

}

10101

10111

00111

10101

10111

00111

1010110111

00111

10101

10111

00111

10101

10111

00111

10101

10111

00111

Gotcha!!!!






Gotcha!!!!



{

char c;

printf("%c\n", c);return 0;

}

10101

10111

00111

10101

10111

00111

1010110111

00111

10101

10111

00111

10101

10111

00111

10101

10111

00111

µ

Gotcha!!!!






Gotcha!!!!



{

int i = 0;

printf("%d\n", i);return 0;

}

10101

10111

00111

10101

10111

00111

1010110111

00111

10101

10111

00111

10101

10111

00111

10101

10111

00111

Gotcha!!!!






Gotcha!!!!



{

int i = 0;

printf("%d\n", i);return 0;

}

10101

10111

00111

10101

10111

00111

0000000000

00000

10101

10111

00111

10101

10111

00111

10101

10111

00111






Programming

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Programming in C - 05 - Variables

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