Input/Output in C

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Section 2.8 Input/Output in C

Checkpoint 2.8.1. Format descriptors.

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

%f
float
%g
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

Checkpoint 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

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Section 2.8 Input/Output in C

Checkpoint 2.8.1. Format descriptors.

Checkpoint 2.8.2. Parsons Problem: File I/O.