K & R C Programs Exercise 5-11.

K and R C, Solution to Exercise 5-11:
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 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. Read more about C Programming Language .

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#define MAXLINE 100
#define TABINC 8
#define YES 1
#define NO 0
void settab(int argc , char *argv[], char *tab);
void entab(char *tab);
void detab(char *tab);
int tabpos(int pos, char *tab);

main(int argc, char *argv[])
char tab[MAXLINE + 1];
settab(argc, argv, tab);
settab(argc, argv, tab);
return 0;

/*entab: replace strings of blanks with tabs and blanks */
void entab(char *tab)
int c, pos;
int nb = 0;
int nt = 0;
for(pos = 1;(c=getchar()) != EOF;pos++)

if(c == ' '){
if(tabpos(pos, tab) == NO)
nb = 0;
}else {
for(;nt > 0;nt--)
if (c == 't')
nb = 0;
for(;nb > 0;nb--)
putchar(' ');
if(c == 'n')
pos = 0;
else if(c == 't')
while (tabpos(pos(pos, tab) != YES)

/*detab:replace tab with blanks*/
void detab(char *tab)
int c,pos = 1;
while ((c = getchar()) != EOF)
if (c == 't') {
putchar(' ');
while (tabpos(pos++, tab) != YES);
}else if(c == 'n'){
pos = 1;

//setab: set tab stops in array tab
void settab(int argc, char *argv[], char *tab)
int i, pos;
if (argc <= 1)
for(i = 1; i <= MAXLINE; i++)
if(i % TABINC == 0)
tab[i] = YES;
else tab[i] = NO;
for(i = 1;i <= MAXLINE; i++)
tab[i] = NO;
while(--argc > 0){
pos = atoi(*++argv);
if(pos > 0 && pos <= MAXLINE)
tab[pos] = YES;

//tabpos: determine if pos is at a tab stop
int tabpos(int pos, char *tab)
if (pos > MAXLINE)
return YES;
return tab[pos];

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