C Programming mock test: free online practice

What does the C Programming mock test cover?

The test covers 12 topics across three levels. Each attempt picks 15 to 30 questions at random, by the level you choose, so every attempt is different.

• Dynamic Memory
• Pointers
• Strings
• Structures and Unions
• Arrays
• Control Flow
• Data Types and Operators
• Preprocessor and Macros
• Bitwise Operations
• File Handling
• Functions and Recursion
• Storage Classes and Scope

Sample C Programming mock test questions

One question from each level, the way they appear in the test. A new set comes on the 1st of every month. Try it, then open the answer.

1. FresherStructures and Unions

   Which operator reads a member through a pointer to a structure, as in a pointer emp to struct employee?

   • ::
   • &
   • .
   • ->
   Show the answer

   Answer: ->. emp->salary is shorthand for (*emp).salary: it follows the pointer and then picks the member. The dot operator is for a struct variable itself. :: belongs to C++, and & takes an address.

2. Intermediate (1-5 years)File Handling

   Priya writes progress lines with fprintf(fp, ...), but after the program crashes the file is empty. What is the most likely reason?

   • The disk refused the writes
   • The output was still in the stdio buffer in memory and was never flushed to the file
   • fprintf writes only when the file is opened in binary mode
   • fprintf needs a newline to write anything at all
   Show the answer

   Answer: The output was still in the stdio buffer in memory and was never flushed to the file. Files are fully buffered by default, so data reaches the file only when the buffer fills, on fflush or on fclose. A crash loses the buffer. Call fflush(fp) after important lines, or use setvbuf to change buffering.

3. Experienced (5+ years)Pointers

   On 64-bit Linux with GCC, what does this code print?

   struct pkt {
       int id;
       double v;
   };
   struct pkt a[4];
   char *b = (char *)&a[0];
   char *e = (char *)&a[3];
   printf("%td %td\n", &a[3] - &a[0], e - b);

   • 3 36
   • 3 3
   • 3 48
   • 48 48
   Show the answer

   Answer: 3 48. Subtracting struct pointers counts elements, so the first value is 3. Through char pointers it counts bytes: struct pkt is 16 bytes (4-byte id, 4 padding, 8-byte double), so 3 elements are 48 bytes.

Take the full C Programming mock test: 15 to 30 questions and 15 to 30 minutes, by level.

How is the C Programming mock test scored?

A question counts as right only when you pick exactly the right option, or all the right options where it says so; a question left blank counts as wrong. Your score is the share of the test's questions you got right (15 to 30, by level). The result also scores every topic, so you know what to revise before the interview.

• 75% or more in a topica strength
• 50% to 74%worth a revision
• Under 50%a topic to work on