C

Question 1

What is the main method in C?

Answer 1

-Starting point of your C application
-Returns an int
-If returned value is not provided, defaults to return 0

Question 2

What is 0 indicate by convention?

Answer 2

Valid exit

Question 3

What does a non-zero indicated by convention

Answer 3

Some kind of error to the calling program

Question 4

What are C programs complied into?

Answer 4

Object code by a compiler

Question 5

What does the pre-processor cpp do ?

Answer 5

It examines the source code before the compiler:
-it identifies any special cpp directives
-it re-writes source code into an intermediate source file
-it passes the new source file to the compiler

Question 6

What are the 3 forms of cpp directives?

Answer 6

1.File inclusion:
-#include <file>: paste a file directly into your source code
2.Macros:
-#define <content>: these are pure textual substitutions
3.Conditional inclusions:
-#ifndel <label></label></content></file>

Question 7

What is important to remember about cpp directives?

Answer 7

They are not part of the C language. Gcc never knows anything about them, because it only sees the extended output created by cpp.

Question 8

What is an example of a standard header file ?

Answer 8

stdio.h

Question 9

Why is it important to have header files?

Answer 9

They contain declarations for various functions–> declarations provide basic type information for the compiler.
Since the compiler compiles each source file independently, it does not know that this function is properly defined in another source file.

Question 10

What does #include <stdio.h> do?</stdio.h>

Answer 10

It includes a declaration for the printf() function

Question 11

What is the error “Symbol could not be resolved” mean?

Answer 11

You have probably forgotten the associated header file.

Question 12

What is the basic form use of printf()?

Answer 12

printf(formatting string, variable list);

Question 13

What are the 5 main C data types?

Answer 13

d :decimal integer
f :floating point value
s :character string
c :individual character
p :pointer address value

Question 14

C is a … language?

Answer 14

An imperative, procedural language

Question 15

What are imperative languages?

Answer 15

They use a series of statements, each of which can modify the state of the program.

Question 16

What is the difference between imperative and declarative languages?

Answer 16

Imperative –> HOW to produce its output
Declarative(SQL)–> WHAT output you would like to see

Question 17

What is a procedural language?

Answer 17

It indicates that programming logic can be encoded as procedures or sub-routines that can be called from other locations in the code.
MOST BASIC FORM OF STRUCTURED PROGRAMMING

Question 18

What do OO languages do that imperative procedural languages don’t?

Answer 18

OO languages –>use methods to provide sub-routines + couple data with the methods that operate on them.
C IS NOT OBJECT ORIENTED LANGUAGE

Question 19

What is the gcc invocation used for?

Answer 19

To compile several source files into a single executable

Question 20

What is a header guard?

Answer 20

They ensure that only one copy of this header file gets included in your source file.

Question 21

What is the -Wall flag used for?

Answer 21

It prints all warnings

Question 22

What is different about C methods from Java methods?

Answer 22

There are no public/private methods. –> all functions are externally visible
We can use static to tell the compiler that this function can only be referenced/invoked from the source file in which it is written.

Question 23

What is the main difference between C and Java(architecture)?

Answer 23

Java is standardized across all CPU architectures i.e int is always 4 bytes
C isn’t i.e int may be 2,4 or 8 bytes

Question 24

How do we determine the byte count of a given primitive type?

Answer 24

Using sizeof()

Question 25

What is the main difference between C and Java(arrays)?

Answer 25

Java –> bounds checking to make sure you don’t index outside of the array. RUN-TIME ERROR
C–> no bounds checking on arrays

Question 26

How does C compensate for having no classes/data?

Answer 26

Using struct:
-its like a class definition without any methods
* usually included in header files so other functions can use them

Question 27

What are the 3 ways that memory can be set aside for data in C?

Answer 27

1.Static
2.Automatic
3.Dynamic

Question 28

What is static allocation?

Answer 28

-It occurs when the compiler knows that a variable will exist for the lifetime of the program. –> because variable is declared outside of any function
* THERE IS ONLY 1 COPY of this variable so the compiler can set aside memory for this at compile time

Question 29

What is automatic allocation?

Answer 29

-It occurs automatically at run-time
-Used for variables that are defined inside a function
-Exist only while the function is executing
How it works: a run-tike component will set up memory for these variables when the function is called and when the function finishes, all memory is released.

Question 30

What happens if the memory isn’t released when the function finishes in automatic allocation?

Answer 30

Memory leaks:
-if they are produced each time a function is called, a long running program will eventually run out of memory and crash

Question 31

Where is the function memory?

Answer 31

On the process STACK:
-each function has its own stack frame
-in each frame are each of the local variables in the function
-STACK grows and shrinks as the program runs

Question 32

What is dynamic allocation?

Answer 32

-Memory is allocated at run-time only as you ask for it.
-Memory will be taken from a pool of memory called the heap that is set aside for each process.
-The heap grows as required

Question 33

What are the 3 basic basic memory allocation functions?

Answer 33

1.malloc(MOST COMMON) : allocate some number of bytes of uninitialized memory
2.calloc: similar to malloc except it initializes the memory to 0
3.realloc: re-allocate a previous memory block to a new size* used for re-sizing arrays

Question 34

What does * refer to in C?

Answer 34

It refers to a pointer value which is a reference to a memory allocation.

Question 35

What is important to remember about the addresses generated by malloc?

Answer 35

They are logical addresses:
-they represent the relative position of a data element in the current process space.
-not an actual physical address in memory

Question 36

What are the memory regions for all 3 types of allocations?

Answer 36

Static:
-in a fixed location near the bottom of the space
Automatic:
- STACK is at the top of the space and grows downward
Dynamic:
-HEAP is in the lower region of the space and grows upward

Question 37

What happens when you try to access an invalid memory location?

Answer 37

The OS will abort your application and print a segmentation fault error.

Question 38

What is special about manipulation of character strings in C?

Answer 38

Strings are just arrays of characters accessed with a char*
Strings end with a terminating character :
-NULL OR \0
-not part of the string length