Input/Output in C

Section 2.8 Input/Output in C

Exercise 2.8.1. Format Descriptors.

Match the format string to the type of variable it works with in scanf.

%f
float
%lf
double
%d
int
%u
unsigned int
%c
char
%s
a C string (e.g., char *)
%p
an address (e.g. any pointer type, like int *)
%ld
long
%lu
unsigned long
%lld
long long
%llu
unsigned long long

Exercise 2.8.2. Parsons Problem: File I/O.

Put the following lines of code in order to read a single integer value into the variable named population from the file demographics.txt. If the file cannot be opened, the code should print "Error opening file" and then quit with a call to exit().

FILE *infile;
int population;
---
infile = fopen("demographics.txt", "r");
---
if (infile == NULL) {
---
printf("Error opening file.\n");
---
exit(1);
---
}
---
fscanf(infile,"%d", &population);
---
fclose(infile);
---
scanf("%d", &population); #distractor
---
fscanf(infile,"%d", population); #distractor
---
infile = open("demographics.txt", "r"); #distractor
---
infile = fopen("demographics.txt", "w"); #distractor

Exercise 2.8.3. Parsons Problem: File I/O (2).

Write a program that opens a file named "hamlet.txt", and counts how many times the letter h appears in the file (both in lowercase and in uppercase), as well as how many total characters are in the file. The program should then output the following:

The total number of ‘h’ or ‘H’ characters that appear in the file.
The total number of characters in the file.
The percentage of characters in the file are h or H.

Sample output (for the actual play Hamlet):

Count: 8688
Total Count: 182567
Percent H’s: 4.76

#include <stdio.h>
#include <stdlib.h>
---
int main(void) {
---
    FILE *infile;
    int ch, h_count, total_count;
    double percentage;
    total_count = 0;
    h_count = 0;
---
    infile = fopen("hamlet.txt","r"); 
---
    if (infile == NULL) {
	   printf("Error: Could not open file!\n"); 
         exit(1);
    }
---
    while ( (ch = getc(infile)) != EOF ) {
---
        if (ch == 'h' || ch == 'H') {
            h_count++;
        }
---
        total_count++;
    }
---
    percentage = (100 * h_count) / total_count;
---
    printf("H Count: %d\n",  h_count);
    printf("Total Count: %d\n", total_count);
    printf("Percent H's: %2.2f\n", percentage);
    fclose(infile);
    return 0;
}
---
    while ( (ch = getc(infile)) ==  0) { #distractor
---
    while ( (fgets(infile)) != EOF ) { #distractor
---
    infile = open("hamlet.txt","r"); #distractor