H192 Engineering - Computer Programming
Daily Assignment A05 Advanced
Tips and Hints Detecting Errors in the Input Sream & Flushing Characters Out of the Stream
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The Ohio State University Gateway Engineering Education Coalition
P. 1
Engineering H192 - Computer Programming
scanf
If successful, scanf returns the number of items successfully read which will be between 0 and the number variables list in the call to scanf If the input stream is exhausted (at end-of-file), scanf returns an indication of end-of-file, or "EOF" (-1)
returnValue = scanf ("%d%d",&a,&b);
-1 EOF
0 1 Conversion error Got a, error while while scanning for a looking for b
The Ohio State University Gateway Engineering Education Coalition
2 Found both a and b
P. 2
Winter Quarter
Engineering H192 - Computer Programming
scanf Example
#include <stdio.h> int main( ) { int returnValue, a, b, x; for (x = 0 ; x < 3 ; x++) { //Prompt and Get User Input printf ("Enter String: "); returnValue = scanf ("%d%d", &a, &b); //Print Variable Values printf ("\nreturnValue = %d\n", returnValue); printf ("a = %d\n",a); printf ("b = %d\n",b); } }
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Engineering H192 - Computer Programming
Tracing the scanf Example
Enter String:
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P. 4
Engineering H192 - Computer Programming
Tracing the scanf Example
Enter String: 4 5<CR> returnValue = a = b =
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The Ohio State University Gateway Engineering Education Coalition
P. 5
Engineering H192 - Computer Programming
Tracing the scanf Example
Enter String: 4 5<CR> returnValue = 2 a = 4 b = 5
Text in Buffer Before Prompt "" Text in Buffer Before scan "4 5\n" After scanf ("%d%d", &a, &b); "\n"
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The Ohio State University Gateway Engineering Education Coalition
P. 6
Engineering H192 - Computer Programming
Tracing the scanf Example
Enter String: 4 5<CR> returnValue = 2 a = 4 b = 5 Enter String: 6 fish<CR> returnValue = a = b =
Winter Quarter
The Ohio State University Engineering Gateway Education Coalition
P. 7
Engineering H192 - Computer Programming
Tracing the scanf Example
Enter String: 4 5<CR> returnValue = 2 a = 4 b = 5 Enter String: 6 fish<CR> returnValue = 1 a = 6 b = 5
Text in Buffer Before 2nd Prompt "\n" Text in Buffer Before 2nd scan "\n6 fish\n" After 2nd scanf ("%d%d", &a, &b); "fish\n"
b remains unchanged
Winter Quarter
The Ohio State University Gateway Engineering Education Coalition
P. 8
Engineering H192 - Computer Programming
Tracing the scanf Example
Enter String: 4 5<CR> returnValue = 2 a = 4 b = 5 Enter String: 6 fish<CR> returnValue = 1 a = 6 b = 5 Enter String: returnValue = 0 a = 6 b = Quarter 5 Winter
Text in Buffer Before 2nd Prompt "fish\n" Text in Buffer Before 2nd scan "fish\n" After 2nd scanf ("%d%d", &a , &b); "fish\n" Doesn't Wait for Input!!
a & b are unchanged!
The Ohio State University Gateway Engineering Education Coalition P. 9
Engineering H192 - Computer Programming
Getting the "fish\n" Out of the Stream Remove characters one by one while (scanf ("%c", &c) != 0); Once `h' is removed, it prompts for user input while ( getchar( ) != `\n'); Once `h' is removed, it finds `\n' and stops
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