EXAM 2 Topics

Question 1

What is dynamic memory?

Answer 1

Memory that is allocated during runtime (the execution of a program).

Question 2

What is malloc?

Answer 2

Memory allocation. Used to allocate a specified number of bytes of memory. It reserves space.

Question 3

What is calloc?

Answer 3

Contiguous Allocation. Similar to malloc, but it also initializes the allocated memory to 0
Initializes null, gets space on heap and returns and puts all 0s/nulls in space.

Question 4

What is realloc?

Answer 4

Reallocate. Used to resize a previously allocated block of memory. Makes memory bigger or smaller, can’t call realloc on something in stack.

Question 5

What is free?

Answer 5

Deallocates memory previously allocated on heap. One argument, pointer to dynamic memory and return memory back to system.

Question 6

What is a memory leak?

Answer 6

Program allocates memory, but fails to release memory when it isn’t needed. Program holds memory and consumes system resources.

Question 7

What is a dangling pointer?

Answer 7

Pointer that is still pointing to memory location even after it’s been deallocated. Pointer points to unfreed memory. Set pointers to NULL after memory is freed.

Question 8

What are the five main stages in program translation?

Answer 8

Preprocessor, Compiler, Assembler, Linker, Loader

Question 9

What is the lexical analyzer?

Answer 9

Input character stream, outputs token stream. Breaks down into tokens: identifiers, operators, and literals.

Question 10

What is the syntax analyzer?

Answer 10

Input token stream, output syntax tree I. Checks if syntax adheres to rules, output represents program’s structure.

Question 11

What is the Semantic analyzer?

Answer 11

Input syntax tree I, output syntax tree II. Checks for violation of rules.

Question 12

What is the compiler?

Answer 12

Converts human-readable source code into machine executable code. Input C program(.c) output Assembly(.o). CREATES AN ASSEMBLY LANGUAGE PROGRAM.

Question 13

What is the preprocessor process?

Answer 13

Character stream -> Lexical Analyzer -> token stream -> syntax analyzer -> Syntax tree -> Semantic Analyzer-> intermediate code generator

Question 14

What is the assembler?

Answer 14

Input Assembly(.o) output Machine Code. Translates assembly to machine code, converts to binary instructions and memory addresses. CREATES AN OBJECT MODULE.

Question 15

What is the linker?

Answer 15

input Machine Code output Executable Load Module(.exe). Has access to Libraries. ‘Links’ different parts of program together so it is runnable. LINKS ALL OBJECT MODULES INTO AN EXECUTABLE.

Question 16

What is the loader?

Answer 16

Input Executable Load Module(.exe) output Memory. Prepares program in memory to be executable. LOADS THE LINKED EXECUTABLE.

Question 17

What are binary streams?

Answer 17

Raw bytes of data

Question 18

What are text streams?

Answer 18

Each byte represents a character

Question 19

What is buffering?

Answer 19

Collects and manages data in chunks. Efficient, reduces amount of physical input/output.

Question 20

What is an abstract data type?

Answer 20

A description of data structure and operations that can be performed on it. Doesn’t specify details of implementation, just behavior and properties.

Question 21

What are the two types of data structures?

Answer 21

Discrete: ints, chars, bools
Scalar: discrete types, and reals

Question 22

What are the data categories?

Answer 22

Simple, Primitive, Structured, User-defined.

Question 23

What is type checking?

Answer 23

Process of enforcing a languages typing rules.

Question 24

What is a struct?

Answer 24

A user defined data type that lets you group together variables of different data types.

Question 25

What is a union?

Answer 25

Is similar to structure, however all members of the union are stored in the same memory location so only one member can hold a value at a time.

Question 26

What is the comma operator?

Answer 26

’,’ binary operator allows you to evaluate multiple expressions separated by commas.

Question 27

What is binary?

Answer 27

Read from right to left, 1 indicates counted number, 0 indicates uncounted number.
Negative Numbers: Signed bit, first bit in sequence, will be 1. Indicating negative.
Ones Complement: Method of inverting binary number to get complement. Change all 0s to 1s and 1s to 0s.
0 111 +7 → 1 000 -7
Twos Complement: Method for representing both positive and negative integers in binary form. Negative numbers are represented by taking one’s complement, then starting from the right flipping bits until you flip a 0.
0 111 +7 → 1 000(ones complement) → 1 001(twos complement) -7

Question 28

What are the bitwise logical operators?

Answer 28

~ Complement: when inverting bits (0 to 1, 1 to 0)
| OR: when turning on individual bits 1100 | 0010 → 1110
& AND: when testing individual bits x&0001 → non-zero if rightmost of x is 1, masking collections x & 0x000000ff turn upper 24 bits to 0, keep lower 8, turning off individual bits 1110 & ~0100 = 1110 & 1011 → 1010
^ XOR: reversible, simple encryption. Exclusive either/or (i.e no matching)

Question 29

What are bitwise shift operators?

Answer 29

“Pick up” bits and move them left or right by some number of bit positions.
Left shift by N bits: data &laquo_space;N.
Drop N bits from left, fill on right with N new bits.
Right Shift by N bits: data&raquo_space; N.
Drop N bits from right, fill on left with N new bits.

Question 30

What is a preprocessor?

Answer 30

Text replacement, syntax analysis, lexical analysis, etc.

Question 31

What is the difference between the top half and bottom half of the compiler?

Answer 31

Top-half: Scanner produces token sequence, parser produces parse tree, semantic analysis produces an intermediate language
Bottom-half: Creates the assembly language program

Question 32

What are the translation steps?

Answer 32

Scan for tokens
Parse
Analyze semantics
Generate assembly instructions
Write Object Module
Link with libraries
Load module into memory

Question 33

The C language is said to pass arrays by _______ because you can change the array’s contents, but it is really pass by _____

Answer 33

reference, value

Question 34

It is not possible to assign to an array variable because its ______ is fixed and immutable

Answer 34

address

Question 35

In order to create an ADT, you have to use a _______to define a name that is ______ to the user

Answer 35

typedef, opaque

Question 36

In C, the ______ file for an ADT module serves as the ______ for the client

Answer 36

header, interface

Question 37

The qualifier _____ makes a name visible only inside the module

Answer 37

static

Question 38

The word _____, when applied as a qualifier to a name of some pointer type, makes it illegal to change the value of the _____

Answer 38

const, pointer

Question 39

g. It is risky to use the _____ function to measure the size of a C string. That will measure the storage size only for a variable whose type is of array char and tell nothing about a pointer to a char memory block. While you cannot tell the size of memory allocated for the string, you can use the ____ function to get the number of significant characters in the string

Answer 39

sizeof, strlen

Question 40

What is a stack?

Answer 40

a linear data structure, a collection of items of the same type.

Question 41

The function _____ is used to open a file and has 2 parameters: the _______ and the _____

Answer 41

fopen, file location, mode

Question 42

The _____ function is used to write to a binary file and the _____ function is used to read from a binary file

Answer 42

fwrite, fread