K & R C Exercise Solutions.

Posted on July 27, 2012June 19, 2017 by Sandeepa Nadahalli

We have already provided solutions to all the exercises in the book “C Programming Language (2nd Edition)“ popularly known as K & R C book.

In this blog post I will give links to all the chapters of the “C Programming Language (2nd Edition)” popularly known as K & R C book for easy reference.

Chapter 1: A Tutorial Introduction

Chapter 2: Types, Operators and Expressions

Chapter 3: Control Flow

Chapter 4: Functions and Program Structure

Chapter 5: Pointers and Arrays

Chapter 6: Structures

Chapter 7: Input and Output

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K & R C Chapter 7 Exercise Solutions.

Posted on May 25, 2012 by Sandeepa Nadahalli

We have already provided solutions to all the exercises in the book “C Programming Language (2nd Edition)“ popularly known as K & R C book.

In this blog post I will give links to all the exercises from Chapter 7 of the book for easy reference.

Chapter 7: Input and Output

Exercise 7-1. Write a program that converts upper case to lower or lower case to upper, depending on the name it is invoked with, as found in argv[0].
Solution to Exercise 7-1.

Exercise 7-2.Write a program that will print arbitrary input in a sensible way. As a minimum, it should print non-graphic characters in octal or hexadecimal according to local custom, and break long text lines.
Solution to Exercise 7-2.

Exercise 7-3.Revise minprintf to handle more of the facilities of printf .
Solution to Exercise 7-3.

Exercise 7-4. Write a private version of scanf analogous to minprintf from the previous section.
Solution to Exercise 7-4.

Exercise 7-5. Rewrite the postfix calculator of Chapter 4 to use scanf and/or sscanf to do the input and number conversion.
Solution to Exercise 7-5.

Exercise 7-6. Write a program to compare two files, printing the first line where they differ.
Solution to Exercise 7-6.
Exercise 7-7. Modify the pattern finding program of Chapter 5 to take its input from a set of named files or, if no files are named as arguments, from the standard input. Should the file name be printed when a matching line is found?
Solution to Exercise 7-7.

Exercise 7-8. Write a program to print a set of files, starting each new one on a new page, with a title and a running page count for each file.
Solution to Exercise 7-8.

Exercise 7-9. Functions like isupper can be implemented to save space or to save time. Explore both possibilities.
Solution to Exercise 7-9.

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K & R C Chapter 6 Exercise Solutions.

Posted on May 10, 2012 by Sandeepa Nadahalli

We have already provided solutions to all the exercises in the book “C Programming Language (2nd Edition)“ popularly known as K & R C book.

In this blog post I will give links to all the exercises from Chapter 6 of the book for easy reference.

Chapter 6: Structures

Exercise 6-1. Our version of getword does not properly handle underscores, string constants, comments, or preprocessor control lines. Write a better version.
Solution to Exercise 6-1.

Exercise 6-2.Write a program that reads a C program and prints in alphabetical order each group of variable names that are identical in the first 6 characters but different somewhere thereafter. Don’t count words within strings and comments. Make 6 a parameter that can be set from the command line.
Solution to Exercise 6-2.

Exercise 6-3.Write a cross-referencer that prints a list of all words in a document, and, for each word, a list of the line numbers on which it occurs. Remove noise words like “the,” “and,” and so on.
Solution to Exercise 6-3.

Exercise 6-4. Write a program that prints the distinct words in its input sorted into decreasing order of frequency of occurrence. Precede each word by its count.
Solution to Exercise 6-4.

Exercise 6-5. Write a function undef that will remove a name and definition from the table maintained by lookup and install .
Solution to Exercise 6-5.

Exercise 6-6. Implement a simple version of the #define processor (i.e., no arguments) suitable for use with C programs, based on the routines of this section. You may also find getch and ungetch helpful.
Solution to Exercise 6-6.

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K & R C Chapter 5 Exercise Solutions.

Posted on May 4, 2012 by Sandeepa Nadahalli

We have already provided solutions to all the exercises in the book “C Programming Language (2nd Edition)“ popularly known as K & R C book.

In this blog post I will give links to all the exercises from Chapter 5 of the book for easy reference.

Chapter 5: Pointers and Arrays

Exercise 5-1. As written, getint treats a + or – not followed by a digit as a valid representation of zero. Fix it to push such a character back on the input.
Solution to Exercise 5-1.

Exercise 5-2.Write getfloat , the floating-point analog of getint . What type does getfloat return as its function value?
Solution to Exercise 5-2.

Exercise 5-3.GWrite a pointer version of the function strcat that we showed in Chapter 2: strcat(s,t) copies the string t to the end of s .
Solution to Exercise 5-3.

Exercise 5-4. Write the function strend(s,t) , which returns 1 if the string t occurs at the end of the string s , and zero otherwise.
Solution to Exercise 5-4.

Exercise 5-5. Write versions of the library functions strncpy , strncat , and strncmp , which operate on at most the first n characters of their argument strings. For example, strncpy(s,t,n) copies at most n characters of t to s . Full descriptions are in Appendix B.
Solution to Exercise 5-5.

Exercise 5-6. Rewrite appropriate programs from earlier chapters and exercises with pointers instead of array indexing. Good possibilities include getline (Chapters 1 and 4), atoi , itoa , and their variants (Chapters 2, 3, and 4), reverse (Chapter 3), and strindex and getop (Chapter 4).
Solution to Exercise 5-6.
Exercise 5-7. Rewrite readlines to store lines in an array supplied by main , rather than calling alloc to maintain storage. How much faster is the program?
Solution to Exercise 5-7.

Exercise 5-8.There is no error-checking in day_of_year or month_day. Remedy this defect.
Solution to Exercise 5-8.

Exercise 5-9.Rewrite the routines day_of_year and month_day with pointers instead of indexing.
Solution to Exercise 5-9.

Exercise 5-10. Write the program expr , which evaluates a reverse Polish expression from the command line, where each operator or operand is a separate argument. For example, expr 2 3 4 + * evaluates 2 X (3+4).
Solution to Exercise 5-10.

Exercise 5-11. Modify the programs entab and detab (written as exercises in Chapter 1) to accept a list of tab stops as arguments. Use the default tab settings if there are no arguments.
Solution to Exercise 5-11.

Exercise 5-12. Extend entab and detab to accept the shorthand entab -m +n to mean tab stops every n columns, starting at column m . Choose convenient (for the user) default behavior.
Solution to Exercise 5-12.

Exercise 5-13. Write the program tail, which prints the last n lines of its input. By default, n is 10, say, but it can be changed by an optional argument, so that tail -n prints the last n lines. The program should behave rationally no matter how unreasonable the input or the value of n. Write the program so it makes the best use of available storage; lines should be stored as in the sorting program of Section 5.6, not in a two-dimensional array of fixed size.
Solution to Exercise 5-13.

Exercise 5-14. Modify the sort program to handle a -r flag, which indicates sorting in reverse (decreasing) order. Be sure that -r works with -n.
Solution to Exercise 5-14.
Exercise 5-15.Add the option -f to fold upper and lower case together, so that case distinctions are not made during sorting; for example, a and A compare equal.
Solution to Exercise 5-15.

Exercise 5-16.Add the -d (“directory order”) option, which makes comparisons only on letters, numbers and blanks. Make sure it works in conjunction with -f .
Solution to Exercise 5-16.

Exercise 5-17. Add a field-handling capability, so sorting may be done on fields within lines, each field sorted according to an independent set of options. (The index for this book was sorted with -df for the index category and -n for the page numbers.)
Solution to Exercise 5-10.

Exercise 5-18. Make dcl recover from input errors.
Solution to Exercise 5-18.

Exercise 5-19. Modify undcl so that it does not add redundant parentheses to declarations.
Solution to Exercise 5-19.

Exercise 5-20. Expand dcl to handle declarations with function argument types, qualifiers like const , and so on.
Solution to Exercise 5-20.

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K & R C Programs Exercise 7-9.

Posted on February 7, 2012 by Sandeepa Nadahalli

K and R C, Solution to Exercise 7-9:
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 Functions like isupper() can be implemented to save space or to save time. Explore both possibilities. Read more about C Programming Language .isupper: return 1 (true) if c is an upper case letter
Normal C function:

int  isupper(char c)
{
if (c >= 'A' && c <= 'Z')
 return 1;
else
 return 0;
}

This simple code tests the character is upper or lower , If the character within the range of ASCII upper case letters it returns 1, otherwise 0.
To save space or to save time using the macros is the best possibility
C Code:

#define isupper(c)  ((c) > = 'A' && (c) <= 'Z') ? 1:0

Macro version of isupper is more efficient because, there is no overhead of the function call and it uses more space because the macro is expanded in line every time it is invoked.

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K & R C Programs Exercise 7-8.

Posted on February 7, 2012 by Sandeepa Nadahalli

K and R C, Solution to Exercise 7-8:
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 print a set of files, starting each new one on a new page, with a title and running page for each file 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 [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<stdlib.h>

#define MAXBOT 3
#define MAXHDR 5
#define MAXLINE 100
#define MAXPAGE 66

/*print: print files - each new one on a new page  */
main(int argc, char *argv[])
{

 FILE *fp;
 void fileprint(FILE *fp, char *fname);

 if(argc == 1)
  fileprint(stdin," ");
 else
  if((fp = fopen(*++argv,"r")) == NULL) {
   fprintf(stderr,"find:can't open %sn",*argv);
   exit(1);
  } else {

   fileprint(fp, *argv);
   fclose(fp);
  }
 return 0;
}


//fileprint: print file name
void fileprint(FILE *fp, char *fname)
{
 int lineno, pageno = 1;
 char line[MAXLINE];
 int heading(char *fname, int pageno);
 lineno = heading(fname, pageno++);
 while(fgets(line, MAXLINE, fp) != NULL) {
  if(lineno == 1) {
   fprintf(stdout,"f");
   lineno = heading(fname, pageno++);
  }
  fputs(line, stdout);
  if(++lineno > MAXPAGE - MAXBOT)
   lineno = 1;
 }
 fprintf(stdout,"f");
}

//heading: put heading and enough blank lines
int heading(char *fname, int pageno)
{
 int ln = 3;
 fprintf(stdout,"nn");
 fprintf(stdout,"%s page %dn", fname, pageno);
 while(ln++ < MAXHDR)
  fprintf(stdout,"n");
 return ln;
}

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K & R C Programs Exercise 7-7.

Posted on February 7, 2012 by Sandeepa Nadahalli

K and R C, Solution to Exercise 7-7:
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 pattern-finding program of chapter 5(C Programming Language 2nd Edition, page no 117.) to take its input from a set of named files or, if no files are named as arguments, from the standard input. Should the file name be printed when a matching line is found.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 [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

#define MAXLINE 1000

/*print lines that match pattern from 1st argument */
main(int argc, char *argv[])
{
 char pattern[MAXLINE];
 int c, excpet = 0,number = 0;
 FILE *fp;
 void fpat(FILE *fp, char *fname, char *pattern, int except, int number);

 while(--argc > 0 && (*++argv)[0] == '-')
  while(c = *++argv[0])
   switch(c) {
   case 'x':
    except = 1;
    break;
   case 'n':
    number = 1;
    break;
   default:
    printf("find:illigal option %cn",c);
    argc = 0;
    break;
   }
 if(argc >= 1)
  strcpy(pattern, *argv);
 else{
  printf("Usage:find[-x] [-n] pattern [file....]n");
  exit(1);
 }
 if(argc == 1)
  fpat(stdin,"",pattern,except,number);
 else
  while(--argc > 0)
   if((fp = fopen(*++argv,"r")) == NULL) {
    fprintf(stderr,"find:can't open %sn",*argv);
    exit(1);
   } else {
    fpat(fp, *argv, pattern,except,number);
    fclose(fp);}
 return 0;
}

/*fpat: find pattern*/
void fpat(FILE *fp, char *fname, char *pattern, int except, int number)
{
 char line[MAXLINE];
 long loneno = 0;

 while(fgets(line, MAXLINE, fp) != NULL){
  ++lineno;
  if((strstr(line,pattern) != NULL) !=except) {
   if(*fname)
    printf("%s -",fname);
   if(number)
    printf("%ld: ",lineno);
   printf("%s",line);
  }
 }
}

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K & R C Programs Exercise 7-6.

Posted on February 7, 2012 by Sandeepa Nadahalli

K and R C, Solution to Exercise 7-6:
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 compare two files, printing the first line where they differ.
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 [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define MAXLINE 100
/*comp: compare two file, printing the first line where they differ*/
main(int argc, char *argv[])
{
 FILE *fp1, *fp2;
 void filecomp(FILE *fp1, FILE *fp2);
 if(argc != 3){
  fprintf(stderr,"comp:need two file namesn");
  exit(1);
 } else {
  if((fp1 = fopen(*++argv, "r")) == NULL) {
   fprintf(stderr, "comp:can't open %sn",*argv);
   exit(1);
  } else if((fp2 = fopen(*++argv, "r")) == NULL) {
   fprintf(stderr, "comp:can't open %sn",*argv);
   exit(1);
  }else  {
   filecomp(fp1,fp2);
   fclose(fp1);
   fclose(fp2);
   exit(0);

  }
 }
}

//filecomp: compare two files -a line at a time
void filecomp (FILE *fp1, FILE *fp2)
{
 char line1[MAXLINE], line2[MAXLINE];
 char *lp1 = *lp2;
 do{
  lp1 = fgets(line1, MAXLINE, fp1);
  lp2 = fgets(line2, MAXLINE, fp2);
  if(lp1 == line1 && lp2 == line2){

   if(strcmp(line1,line2) !=0) {
    printf("First difference in linen%sn",line1);
    lp1 = lp2 = NULL;
   }
  } else if(lp1 != line1 && lp2 == line2)
   printf("end of first file at linen%sn",line2);
  else if(lp1 == line1 && lp2 == line2)
   printf("end of second file at line n%sn",line1);

 }while(lp1 == line1 && lp2 == line2);
}

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K & R C Programs Exercise 7-5.

Posted on February 7, 2012 by Sandeepa Nadahalli

K and R C, Solution to Exercise 7-5:
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.
Rewrite the postfix calculator of chapter 4 to use scanf and/or sscanf to do the input number conversion.
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 [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/



#include<stdio.h>
#include<math.h>       /*for atof()*/
#define MAXTOP 100     /* max size of operand or operator  */
#define NUMBER  '0'    /* SIGNAL THAT A NUMBER WAS FOUND   */
#define MAXVAL 100
int gettop(char []);
void push(double);
double pop(void);
int sp = 0;          /* Next free stack position. */
double val[MAXVAL];  


//reverse Polish calulator
int main(void)
{
 int type;
 double op2;
 char s[MAXOP];

 while((type = getop(s)) != EOF)
 {
  switch(type)
  {
  case NUMBER:
   push(atof(s));
   break;
  case '+':
   push(pop() + pop());
   break;
  case '*':
   push(pop() * pop());
   break;

  case '-':
   op2=pop();
   push(pop() - op2);
   break;
  case '-':
   op2=pop();
   if(op2 != 0.0)
    push(pop() / op2);
   else printf("nError: Zero divissorn");
   break;
  case '%':
   op2 = pop();
   if(op2)
    push(fmod(pop(), op2));
   else
    printf("nError: Division by zero!");
   break;
  case 'n':
   printf("t%.8gn",pop());
   break; 
  default:
   printf("error: unknown command %sn", s);
   break;

  }
 }
 return 0;
}




/* Getop: get next operator or numeric operand. */
int getop(char s[])
{

 int i = 0;
 int c;
 int rc;
 static char lastc[] = " ";
 sscanf(lastc,"%c", &c);
 lastc[0] = ' ';

 /* Skip whitespace */
 while((s[0] = c ) == ' ' || c == 't')
  if(scanf("%",&c) == EOF)
   c = EOF;
 s[1] = '';

 /* Not a number but may contain a unary minus. */
 if(!isdigit(c) && c != '.' )
  return c;               


 if(isdigit(c))
  do{
   rc = scanf("%c",&c);
   if(!isdigit(s[++i] = c))
    break;
  }while(rc != EOF)

   if(c == '.')
    do{
     rc = scanf("%c",&c);
     if(!isdigit(s[++i] = c))
      break;
    }while(rc != EOF)

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

}



/* push: push f onto stack. */
void push(double f)
{
 if(sp < MAXVAL)
  val[sp++] = f;
 else
  printf("nError: stack full can't push %gn", f);
}

/*pop: pop and return top value from stack.*/
double pop(void)
{
 if(sp > 0)
  return val[--sp];
 else
 {
  printf("nError: stack emptyn");
  return 0.0;
 }
}

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K & R C Programs Exercise 7-4.

Posted on February 7, 2012 by Sandeepa Nadahalli

K and R C, Solution to Exercise 7-4:
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 private version of scanf analogous to minprintf from the previous section.
minscanf is similar to minprintf. This function collects characters from the format string until it finds an alphabetic character after a %. That is the localfmt passsed to scanf along with the appropriate pointer.
The arguments to scanf are pointers: a pointer to a format string and a pointer to the variable that receives the value from scanf.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 [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include <stdarg.h>
#include <stdio.h>
#include <ctype.h>
#define LOCALFMT 100

/* minscanf:  minimal scanf with variable argument list */
void minscanf(char *fmt, ...)
{
 va_list ap;
 char *p, *sval;
 char localfmt[LOCALFMT];
 int i,c;
 int *ival;
 double *dval;
 unsigned *uval;

 va_start(ap, fmt);    /* make ap point to the first unnamed arg */
 for (p = fmt; *p; p++) {
  if (*p != '%') {
   localfmt[i++] = *p;
   continue;
  }
  i = 0;
  localfmt[i++] = '%';
  while(*p(p+1) && !isalpha(*(p+1)))
   localfmt[i++] = *++p;
  localfmt[i++] = *(p+1);
  localfmt[i] = '/0';
  switch (*++p) {
  case 'd':
  case 'i':
   ival = va_arg(ap, int *);
   scanf(localfmt, ival);
   break;

  case 'u':

  case 'o':

  case 'x':

  case 'X':


  case 'f':
   dval = va_arg(ap, double);
   scanf(localfmt, dval);
   break;

  case 's':
   sval = va_arg(ap, char *);
   scanf(localfmt, sval);
   break;
  default:
   scanf(localfmt);
   break;
  }
  i = 0;
 }
 va_end(ap);
}

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C Program Examples

K and R-C Programs Exercise

K & R C Exercise Solutions.

K & R C Chapter 7 Exercise Solutions.

K & R C Chapter 6 Exercise Solutions.

K & R C Chapter 5 Exercise Solutions.

K & R C Programs Exercise 7-9.

K & R C Programs Exercise 7-8.

K & R C Programs Exercise 7-7.

K & R C Programs Exercise 7-6.

K & R C Programs Exercise 7-5.

K & R C Programs Exercise 7-4.