Intensive Programming Final

= assigns; == compares

What is the difference between = and == in C?

Declaration tells the compiler the type; definition allocates storage

What is a declaration vs definition?

Value cannot be modified through that identifier

What does const mean?

Variable keeps its value between calls

What does static mean inside a function?

Visible only in that file (internal linkage)

What does static mean at global scope?

A variable that stores a memory address

What is a pointer?

& gets address; * dereferences.

What do & and * mean?

Adding 1 moves by the size of the pointed-to type.

Pointer arithmetic rule?

Indicates "no valid address."

Null pointer purpose?

char * is a pointer; char[] is a fixed array. Arrays cannot be reassigned.

Difference between char *s and char s[]?

void* pointing to allocated memory; NULL on failure.

What does malloc return?

Portable across systems.

Why use sizeof(type) instead of a number?

Memory leak.

What happens if you forget free?

Pointer to freed memory.

What is a dangling pointer?

No bounds checking — can overflow buffer

Why is strcpy dangerous?

Measures visible characters only.

Why strlen(s) doesn't count '\0'?

Compiler inserts bytes to align fields for performance.

What is padding?

ptr->field

How to access struct members through a pointer?

fopen = buffered stdio; open = low-level system call.

Difference between fopen and open?

Number of bytes read or 0 (EOF) or -1 (error).

What does read() return?

No formatting overhead.

Why is system call I/O faster for large files?

Moves file offset (random access).

What does lseek do?

0 to child, child's PID to parent, -1 on error.

What does fork() return?

Two — parent and child.

After fork(), how many processes run?

Child receives a copy of the parent's address space (copy-on-write).

Why is code duplicated after fork()?

Parent waits for specific child to finish.

What does waitpid(pid, &status, 0) do?

WEXITSTATUS(status).

How to get child’s exit code?

Replaces current process image with a new program

What does exec() do?

Nothing returns — the original code is gone.

What happens after successful exec()?

Child starts a new program.

Why call exec() after fork()?

Asynchronous notification to a process

What is a signal?

Terminate program

Default SIGINT behavior?

More reliable; portable; supports flags (like SA_RESTART).

Why use sigaction instead of signal?

Function automatically called when signal arrives

What is a signal handler?

Must only use async-safe functions (e.g., write, not printf).

Restrictions in signal handlers?

text, data, stack, heap

What are the 4 main memory sections?

Stack

What grows downward?

Heap

What grows upward?

Data (initialized) or BSS (uninitialized)

Where are globals stored?