## Jan 17, 2012

### K & R C Programs Exercise 5-1.

K and R C, Solution to Exercise 5-1:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
C Program to get next integer from input into space, so that getint treats a + or - not followed by a digit as a valid representation of zero and fix it to push such a character back on the input. Read more about C Programming Language .
```/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
*                      Happy Coding
***********************************************************/

include<ctype.h>

int getch(void);
void ungetch(int);

/* getint:  get next integer from input into *pn */
int getint(int *pn)
{
int c, sign, sawsign;

while (isspace(c = getch()))   /* skip white space */
;
if (!isdigit(c) && c != EOF && c != '+' && c != '-') {
ungetch(c);    /* it's not a number */
return 0;
}
sign = (c == '-') ? -1 : 1;
if (sawsign = (c == '+' || c == '-'))
c = getch();
if (!isdigit(c)) {
ungetch(c);
if (sawsign)
ungetch((sign == -1) ? '-' : '+');
return 0;
}
for (*pn = 0; isdigit(c); c = getch())
*pn = 10 * *pn + (c - '0');
*pn *= sign;
if (c != EOF)
ungetch(c);
return c;
}
```
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## Jan 16, 2012

### K & R C Programs Exercise 4-14.

K and R C, Solution to Exercise 4-14:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
Write C Program to swap two arguments using macros.
C Program to swap(t, x, y) that interchanges two arguments of type t using the block structure.

```/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
*                      Happy Coding
***********************************************************/

#include <stdio.h>

#define swap(t, x, y) \
do { \
t safe ## x ## y; \
safe ## x ## y = x; \
x = y; \
y = safe ## x ## y; \
} while (0)

int main(void) {
int inum1, inum2;
double dnum1, dnum2;
char *ch1, *ch2;
printf("\nEnter two Intgers:\n");
scanf("%d%d",&inum1,&inum2);
printf("\nIntegers before swap:\n inum1= %d\n inum2= %d\n", inum1, inum2);
swap(int, inum1, inum2);
printf("\nIntegers after swap:\n inum1= %d\n inum2= %d\n", inum1, inum2);

printf("\nEnter two Doubles:\n");
scanf("%f%f",&dnum1,&dnum2);
printf("\nDoubles before swap:\n dnum1= %g\n dnum2= %g\n", dnum1, dnum2);
swap(double, dnum1, dnum2);
printf("\nDoubles after swap:\n dnum1= %g\n dnum2= %g\n", dnum1, dnum2);

printf("\nEnter two Strings:\n");
scanf("%s%s",ch1,ch2);
printf("\n Strings before swap:\n ch1= %s\n ch2 = %s\n", ch1, ch2);
swap(char *, ch1, ch2);
printf("\nStrings after swap:\n ch1= %s\n ch2= %s\n", ch1, ch2);

return 0;
}
```
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### K & R C Programs Exercise 4-13.

K and R C, Solution to Exercise 4-13:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
Write a C Program to reverse the string using the recursive methods.
In this program reverse determines the length of the string and then calls the reverser, which reverses the string s in place. Read more about C Programming Language .

```/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
*                      Happy Coding
***********************************************************/
#include<stdio.h>
/* reverse: reverse the string s in place */
void reverse(char s[])
{

void reverser(char s[], int i, int len);
reverser(s,0,strlen(s));
}

/* reverser: reverse string s in place recursive */
void reverser(char s[], int i, int len)
{
int c, j;
j = len - (i + 1);
if(i < j)
{
c = s[i];
s[i] = s[j];
s[j] = c;
reverser(s, ++i, len);
}
}

```
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### K & R C Programs Exercise 4-12.

K and R C, Solution to Exercise 4-12:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
Write a C program to convert an integer into a string by calling a recursive routine.Recursive routine is the programming technique that a routine invoking itself again and again. Read more about C Programming Language .

```/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
*                      Happy Coding
***********************************************************/

#include<math.h>
void itoa(int n, char s[]);
int main(void) {
char buffer[20];

//for testing!
printf("INT_MIN: %d\n", INT_MIN);
itoa(INT_MIN, buffer);
printf("Buffer : %s\n", buffer);

return 0;
}
/* itoa: convert n to characters in s; recursive */
void itoa(int n, char s[])
{
static int i;
if(n / 10)
itoa(n /10, s);
else{
i = 0;
if(n < 0)
s[i++] = '-';
}
s[i++] = abs(n) %10 + '0';
s[i] = '\0';
}

```
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### K & R C Programs Exercise 4-11.

K and R C, Solution to Exercise 4-11:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
C Program to modify the K & R C Programs Exercise 4-3, Modify the gettop function so that it doesn't need to use ungetch by using internal static variable. Read more about C Programming Language .

```/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<ctype.h>
#define NUMBER '0'

int getch(void);

/* getop: get next operator or numeric operand. */
int getop(char s[])
{
int i ;
int c;
static int lastc = 0;

if(lastc == 0)
c = getch();
else{
c = lastc;
lastc = 0;
}

while((s[0] = c) == ' ' || c == '\t')
c = getch();
s[1] = '\0';

if(!isdigit(c) && c != '.')
return c;
i = 0;
if(isdigit(c))
while(isdigit(s[++i] = c = getch()))
;
if(c == '.')

while(isdigit(s[++i] = c = getch()))
;

s[i] = '\0';
if(c != EOF)
lastc = c;
return NUMBER;

}
```
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### C Program to find sum and product using macros.

Write C Program to find sum and product using macros.
Macro is a piece of text that is expanded by the preprocessor part of the compiler. This is used in to expand text before compiling. Macro definitions (#define), and conditional inclusion (#if). In many C implementations, it is a separate program invoked by the compiler as the first part of translation.Read more about C Programming Language .

```/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#define SUM(A, B) (A + B)
#define PROD(A, B) (A * B)
int main()
{
int num1, num2, sum, product;
printf("\nEnter the Two numbers\n");
scanf("%d%d",&num1,&num2);
sum=SUM(num1,num2);
product=PROD(num1,num2);
printf("\n\nSum of two numbers using Macros is:%d\n",sum);
printf("\n\nProduct of two numbers using macros is:%d\n",product);
return 0;
}
```
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Number System```
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