C Programming: Function Pointers, Operators, and Memory

Flashcards covering key concepts from the Week 3 Lecture 2 on C programming, including function pointers, typedefs, array types, the sizeof operator, and logical operator lazy evaluation.

What are two practical use cases for function pointers mentioned in the lecture?

They are used in Graphical User Interfaces (GUIs) to call specific functions when buttons are pressed and in functions like $Qsort$ to allow for different comparative functions.

What does the name of a function represent in C if it is used without parentheses?

It is a pointer to the function's memory location.

How is a pointer to a function that takes two integers and returns an integer declared?

$$int\,(*pointer\_name)(int, int)$$

What is the purpose of using a $typedef$ with function pointers?

It simplifies the syntax of function pointer declarations, making the notation cleaner and easier to read.

Which four arguments are required by the $Qsort$ function?

The array to be sorted, the number of elements in the array, the size of each element, and a pointer to a comparative function.

In the context of $Qsort$, what is the standard signature for a comparative function?

$$int\,compare(const\,void\,*a, const\,void\,*b)$$

What type is defined by the declaration $char\,*var[]$?

An array of character pointers.

What type is defined by the declaration $long\,var[10]$?

An array of $10$ long integers.

What type is defined by the declaration $void\,(*var)(int, double)$?

A pointer to a function that takes an integer and a double and returns nothing ($void$).

What type is defined by the declaration $int\,*(*var[5])()$?

An array of $5$ function pointers that take no arguments and return a pointer to an integer.

What does the $sizeof$ operator return, and when is its result usually determined?

It returns a value of type $size\_t$ representing the size in bytes of the argument's type, usually determined at compile time except for variable length arrays.

What is the value of $sizeof(string)$ if $char\,*string$ was initialized using $malloc(sizeof(char) \times 3)$ on a 64-bit system?

$8$ bytes, because $sizeof$ returns the size of the pointer, not the size of the memory it points to.

What is the return value of $sizeof(string)$ for the declaration $char\,string[] = "hello"$?

$6$, which accounts for the five characters plus the null terminator.

In the expression $f(i++)$, what value is passed to the function?

The old value of $i$ (the value before the increment).

What is the difference between bitwise operators and logical operators in C?

Bitwise operators (like $|$ and $\&$) perform operations on individual bits, while logical operators (like $||$ and $\&\&$) evaluate truth values ($0$ is false, non-zero is true) and use lazy evaluation.

What is 'lazy evaluation' in the context of C logical operators?

C only evaluates as much of a logical expression as is required to determine the final result; for example, a logical OR ($||$) stops if the first term is true.

According to C operator precedence, which has higher precedence: logical AND ($\&\&$) or logical OR ($||$)?

Logical AND ($\&\&$) has one level higher precedence than logical OR ($||$).

What character is used for the Bitwise OR operation in C?

The vertical bar or pipe symbol ($|$).