Compiling the following problem with visual studio 2000 gives the errors:

temp.obj : error LNK2001: unresolved external symbol "void __cdecl ungetch(int)" (?ungetch@@YAXH@Z)

temp.obj : error LNK2001: unresolved external symbol "int __cdecl getch(void)" (?getch@@YAHXZ)

Debug/temp.exe : fatal error LNK1120: 2 unresolved externals

Error executing link.exe.

The code is taken from Dennis Ritchie's "C Programming Language" 's page 97 (2nd Edition).

C Syntax (Toggle Plain Text)

#include<stdio.h>
#include<ctype.h>
 
int getch(void);
void ungetch(int);
 
int getint(int *pn)
{
	int c, sign;
 
	while (isspace(c=getch()));
 
	if(!isdigit(c) && c != EOF && c != '+' && c != '-')
	{
		ungetch(c);
		return 0;
	}
 
	sign = ( c == '-') ? -1 : 1;
 
	if( c== '+' || c == '-')
		c = getch();
 
	for( *pn = 0; isdigit(c); c = getch())
		*pn = 10 * *pn + (c - '0');
 
	*pn *= sign;
 
	if (c != EOF) ungetch(c);
 
	return c;
}
 
int main()
{
	int *p;
 
	p = new int[10];
 
	p[0] = 4;
	p[1] = 2;
	p[2] = 6;
	p[3] = 8;
	p[4] = 2;
	p[5] = 1;
	p[6] = 7;
	p[7] = 1;
	p[8] = 2;
	p[9] = 1;
 
	int i = getint(p);
 
	printf("The value is %d", i);
 
	return 0;
}

#include<stdio.h> #include<ctype.h> int getch(void); void ungetch(int); int getint(int *pn) { int c, sign; while (isspace(c=getch())); if(!isdigit(c) && c != EOF && c != '+' && c != '-') { ungetch(c); return 0; } sign = ( c == '-') ? -1 : 1; if( c== '+' || c == '-') c = getch(); for( *pn = 0; isdigit(c); c = getch()) *pn = 10 * *pn + (c - '0'); *pn *= sign; if (c != EOF) ungetch(c); return c; } int main() { int *p; p = new int[10]; p[0] = 4; p[1] = 2; p[2] = 6; p[3] = 8; p[4] = 2; p[5] = 1; p[6] = 7; p[7] = 1; p[8] = 2; p[9] = 1; int i = getint(p); printf("The value is %d", i); return 0; }