System Programming 1 Exam

Front 1

What is a block-structured language?

Back 1

Means that things are enclosed inside braces, things are aware of things outside of their own braces, but not of things in braces that are not within their scope.

Front 2

What is a program? What are the type of ``globals'' in a program?

Back 2

functions, variables

Front 3

What does the C Preprocessor do?

Back 3

1) Trigraph Replacement - The preprocessor replaces trigraph sequences with the characters they represent.
2 Line Splicing - Physical source lines that are continued with escaped newline sequences are spliced to form logical lines.
3 Tokenization - The preprocessor breaks the result into preprocessing tokens and whitespace. It replaces comments with whitespace.
4 Macro Expansion and Directive Handling - Preprocessing directive lines, including file inclusion and conditional compilation, are executed. The preprocessor simultaneously expands macros and, in the 1999 version of the C standard, handles _Pragma operators

Front 4

how do you do file inclusion?

Back 4

#include <filename> searches the libraries for the file named.
#include "filename" is dependent, but ussually searches your current directory first, and then the library, for a file name.

Front 5

What are the two macros?

Back 5

#define name stuff - when this is compilled all things with name will be replaced with stuff. Any text can be substituted. You can also define things that look just like functions due to this.
#undef name - undefines the macro called name

Front 6

conditional compilation:

Back 6

#ifdef symbol - is this symbol defined?
#ifndef symbol - is this symbol defined?
#if constant-expression
statements
#endif

Front 7

what are the integer types?

Back 7

char - 1 byte
int <= short (short int) <=
long (long int)
(ussually, short 16,int 16, long 32)

Front 8

floating:

Back 8

float, double
specifies a floating point number of either single precision or double precision.

Front 9

pointer to base_type

Back 9

Pointers contain a location in memory rather than a actual value.Pointers point to a place rather than a thing, think address vs house.

Front 10

compound:

Back 10

arrays (type name[size];)- sequence of contiguous bytes in memory.
structs (struct tag {member-list} variable-list;) hold aggregate amounts of data

Front 11

what are string's in C?

Back 11

really just arrays of char terminated by a null character.

Front 12

what is modifier register?

Back 12

tells the compiler to (if it would) store the variable in register rather than in memory. This may cause faster execution, however, the compiler may ignore your request. Also, you cannot take the address of a register variable.

Front 13

sizes of items (char vs. int, short vs. int, int vs. long, etc.)

Back 13

char is always 1 byte, short must be at least 2, int must be >= short <= long, long must be 4.

Front 14

What does static as a function modfier mean?

Back 14

When used in front of a function declared outside of a block, it changes the linkage from external to internal. Now that function can only be accesed from within the source file they were declared in.

Front 15

equivalence of pointers and arrays

Back 15

Arrays are really just pointers that point to a location and when they are invoked, the pointer is dereferenced and the offset is added to the pointer.

Front 16

What are the types of pointer arithmetic?

Back 16

pointer +/- value - adds/subtracts the size of the data type of the pointer value times.
pointer - pointer - returns the number of sizeOf the pointer elements that are between the two pointers.

Front 17

What are the types of loops in C?

Back 17

for(expression1; expression2; expression3){}
AND
while( expression ) {}
AND
do{}while(expression);

Front 18

What are the decision structures in C?

Back 18

if(expression)
statement
else
statement
AND

switch (expression){
statementA:
break;
statementB:
statementC:
default: <= always if none match
}

Front 19

What are the other non looping and non decision control structures in C?

Back 19

goto label;
AND
fcn(params)

Front 20

What does static as a variable modifier mean?

Back 20

if outside a block, it is identical to the effects on a function with static, if within a block, it means the variable is now static instead of automatic, this means the variable exist from the time the program starts until the end of the program.

Front 21

What does volatile mean as a modifier?

Back 21

volatile informs the compiler that a value may be changed by outside forces. This stops the program from optimizing when it thinks a value cannot have changed.

Front 22

What does const mean as a modifier?

Back 22

constants are exactly like variables except their values cannot be changed.
int *pi; pointer to integer
int const *pci; pointer to constant integer
int * const pci; constant pointer to integer
int const * const pci; constant pointer to constant integer

Front 23

What does unsigned mean as a type modifier?

Back 23

unsigned means that it goes from 0 to 2^n power.

Front 24

what does signed mean as a type modifier?

Back 24

signed means it goes from -(2^n) power to (2^n) power.

Front 25

What does short mean as a type modifier?

Back 25

short means it is smaller or equal to int

Front 26

What does long mean as a type modifier?

Back 26

long means it is greater than or equal to int.

Front 27

What is an expression?

Back 27

anything that is followed by a ';' is an expression.

Front 28

Unary operators?

Back 28

Unary operators are operators that take only one value. such as ! ++ - & sizeOf

Front 29

Binary Operators?

Back 29

any operator that takes two values as arguments.

Front 30

Prefix, Infix, Postfix Operators?

Back 30

Operator appears before, In?, or after the operand.

Front 31

using getc, getchar, fgetc.

Back 31

getc( FILE *stream );//reads from the desired stream on character at a time
fgetc( FILE *stream );//same
getchar();//same but from standard input

Front 32

declaring and calling functions

Back 32

You will first make a prototype of the function before the function is actually declared, this makes the compiler aware of the function at that point. You call a function in a obvious way.

Front 33

parameter passing, returning results

Back 33

all parameters are passed in C pass-by-value, though the effects of this can be confusing at times. returns are also by value

Front 34

Declaring pointers

Back 34

type *name = &typeValue;

Front 35

type casting

Back 35

The (type) operator is called a cast and is used to explicitly convert the value of an expresssion to another type.

Front 36

What are the 4 most common system calls.

Back 36

open close read write

Front 37

Call this system call when you leave a program for some reason.

Back 37

exit();

Front 38

difference between line and block buffering?

Back 38

Line buffering usually delimits on the newline character, block buffering ussually stops when the buffer is full.

Front 39

difference between FILE and file descriptor

Back 39

FILE is a thing used to hold a stream to a currently open file.

Front 40

using fopen and fclose

Back 40

FILE *fopen(char const *name, char const *mode);
*mode can be "r","w","a","rb","wb", "ab"
If function fails NULL value returned.
fclose(FILE *f);
return != 0 if failed.

Front 41

using putc, putchar, fputc

Back 41

int putc( int character, FILE *stream); //puts character on stream
int fputc (int character, FILE *stream); //puts character on stream
int putchar( int character ); // puts character on standard output stream

Front 42

using gets, fgets

Back 42

char *fgets(char *buffer, int buffer_size, FILE *stream);//reads from buffer until buffer_size-1 is same or newline is encountered.NUL appended
char *gets(char *buffer);//same but on standard input

Front 43

using puts, fputs

Back 43

int fputs(char const *buffer, FILE *stream);//writes a nul terminated string to stream. Returns EOF if error occurs.
int puts(char const *buffer);// same but for stdout

Front 44

using printf, fprintf, sprintf

Back 44

int fprintf(FILE *stream, char const *format, ...);//prints acording to format
int printf( char const *format, ...);//same, but with stdout
int sprintf(char *buffer, char const *format, ...);//exact same as fprintf

Front 45

using scanf, fscanf, sscanf

Back 45

int fscanf(FILE *stream, char const *format, ...)//reads from stream until characters in the format could not be matched, number of conversions returned.
int scanf(char const *format, ...);//same but for standard input
int sscanf( char const *string, char const *format, ...);//exact same as fscanf

Front 46

using strlen

Back 46

size_t strlen(char const *string);

returns the number of characters the string contains.
//size_t is an unsigned integer

Front 47

using strcpy, strncpy, strlcpy

Back 47

char *strcpy( char *dst, char const *src);//copies src to dest, returns a pointer to dest array.
strncpy//same but only copies n characters, not null terminatued necesarily.
strlcpy//safer version of strcpy that knows the size

Front 48

using strcat, strncat, strlcat

Back 48

char *strcat( char *dst, char const *src);//appends src to dst, returns a pointer to destination array.
strncat//same, but does insert a nul at the end
strlcat//safeter version of strcat that knows the size

Front 49

using strcmp, strncmp, strcasecmp, strncasecmp

Back 49

int strcmp(char const *s1, char const *s2);
<0 if s1 less than s2, > 0 if s1 is greater than s2, = 0 if se == s2.
strncmp//same, but only compares first n characters
//ignores case

Front 50

how do I access element in command-line argument handling: int main( int argc, char *argv[], char *env[] )

Back 50

*argv gives first command line arguments
argc gives number of arguments first one is the name of the program though