CSC 4630-001: Software Development and Systems

Spring 2013

No C work was included on the lab (it was replaced by some homework). However, two of these four questions will be asked on Exam #1.

• Once I wrote a C program that had these lines in it (among others):

  #include <math.h>
  double answer;
  answer=exp(1.0);	/* this should give me the value of e  */
  

  And yet, gcc produed the following error message when I tried to compile my program:

  Undefined symbol: exp
  

  What's the likely explanation?
• Why was getchar() written so as to return type int, rather than char?
• Explain the two flagged pieces in this fragment:

  while (scanf("%f", &salary)<1){  /* the termination condition here */
        while (getchar()!='\n')    /* this loop */
          ;
        printf("That is not a valid salary.\n");
        printf("Please try again. Enter salary: ");
  }
  

• Look at the bigline.c program below, and explain the terminating conditions in the while loop in main() and in the for loop in the getline() function.

  #include <stdio.h>
  #define MAXLINE 1000  /* maximum input line size */
  
  int getline(char line[], int maxline);
  void copy(char to[], char from[]);
  
  /* print longest input line */
  int main()
  {
  	int len; 	/* current line length */
  	int max;	/* maximum length seen so far */
  	char line[MAXLINE]; /* current input line */
  	char longest[MAXLINE]; /* longest line saved here */
  
  	max = 0;
  	while((len = getline(line, MAXLINE)) > 0)
  		if(len > max) {
  			max = len;
  			copy(longest, line);
  		}
  	if (max > 0) /* there was a line */
  		printf("%s", longest);
  	return 0;
  
  }
  
  /* getline: read a line into s, return length */
  int getline(char s[], int lim)
  {
  	int c, i;
  
  	for(i=0; i<lim-1 && (c=getchar())!=EOF && c!='\n'; i++)
  		s[i]= c;
  	if(c== '\n') {
  		s[i] = c;
  		++i;
  	}	
  	s[i] = '\0';
  	return i;
  	
  }
  
  void copy(char to[], char from[])
  {
  	int i;
  	
  	i = 0;
  	while((to[i] = from[i]) != '\0')		
  		i++;
  }
  
  
  
  

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