c programming - review

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Final Review

Copyright 2008 W. W. Norton & Company.

All rights reserved.1


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When/Where is the final?When:

April 24, 2013 @ 9:30 - 12:00

Where:

A-HS BN-2N (Clara Benson Building) HU-PATE BN-2S (Clara Benson Building) PATI-Z BN-3 (Clara Benson Building)Check Final Exam Schedule for changes




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Post-midterm Topics Arrays Pointers Pointers and Arrays Relationship Strings Structures Dynamic Memory AllocationBook chapters:

1-13 (no recursion), 16 (only structures), 17, 22Copyright 2008 W. W. Norton & Company.



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What to expect? Small questions that test specific parts

Theory; loops, conditionals, number systems, characterarithmetic, arrays, strings, pointers, functions,

structures, memory management, etc. Tracing output

Can include any of the concepts Write a function/program following specifications

Input/Output from keyboard/file Array & String manipulation Pointers Labs & project related




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Chapter 8

Arrays


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One-Dimensional Arrays An array is a data structure containing a number of

data values, all of which have the same type.

To declare an array, we must specify the type of thearrays elements and the number of elements:int a[10];

To access an array element use subscriptingorindexingthe array (an array of length n are indexed from 0 to n 1).




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One-Dimensional Arrays Array initialization

int a[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

int a[10] = {1, 2, 3, 4, 5, 6};

int a[10] = {0};

Expressions of the form a[i] are lvalues, so theycan be used in the same way as ordinary variables:

a[0] = 1;

printf("%d\n", a[5]);

++a[i];




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Multidimensional Arrays An array may have any number of dimensions. The following declaration creates a two-dimensional array

(a matrix, in mathematical terminology):

int m[5][9]; m has 5 rows and 9 columns. Both rows and columns are

indexed from 0:




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Multidimensional Arrays To access the element ofm in row i, column j, we

must write m[i][j].

C stores arrays in row-major order, with row 0first, then row 1, and so forth.

How the m array is stored:




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Multidimensional Arrays Nested for loops are ideal for processing

multidimensional arrays.

Consider the problem of initializing an array for use as anidentity matrix. A pair of nested for loops is perfect:#define N 10

double ident[N][N];int row, col;

for (row = 0; row < N; row++)

for (col = 0; col < N; col++)if (row == col)ident[row][col] = 1.0;

elseident[row][col] = 0.0;




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Random Number GeneratorHow to generate random numbers in a determined

range using rand()?

use the % of the returned value by the range span add the initial value of the range

Examples:

random = rand() % 100; // range 0 to 99

random = rand() % 100 + 1; // range 1 to 100

random = rand() % 30 + 1985; // range 1985-2014




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FUNCTIONS AND ARRAYS




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Functions and Arrays Function prototype with an array as parameter:int sum_array(int a[], int n){}

Function call with array argument:#define LEN 100

int main(void)

{int b[LEN], total;

total = sum_array(b, LEN);

} Copyright 2008 W. W. Norton & Company.All rights reserved.

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Array Arguments A function is allowed to change the elements of an

array parameter, and the change is reflected in the

corresponding argument.

A function that modifies an array by storing zerointo each of its elements:

void store_zeros(int a[], int n){

int i;for (i = 0; i < n; i++)

a[i] = 0;}




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Array Arguments A call ofstore_zeros:store_zeros(b, 100);

The ability to modify the elements of an arrayargument may seem to contradict the fact that C

passes arguments by value.

Chapter 12 explains why theres actually nocontradiction (short answer: pass array arguments

by reference).




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Array Arguments If a parameter is a multidimensional array, only the length

of the first dimension may be omitted.

If we revise sum_array so that a is a two-dimensionalarray, we must specify the number of columns in a:#define LEN 10

intsum_two_dimensional_array(inta[][LEN],intn)

{int i, j, sum = 0;

for (i = 0; i < n; i++)for (j = 0; j < LEN; j++)

sum += a[i][j];

return sum;}




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Example Programs Programs

Reversing a Series of Numbers Checking a Number for Repeated Digits Computing Interest Dealing a Hand of Cards

Functions with Array arguments Print Elements of an Array Reversing the Elements of an Array Bubble Sort




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Chapter 11

Pointers


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Pointer Variables If there are n bytes in memory, we can think of

addresses as numbers that range from 0 to n 1:



Variables in a program

occupy bytes of memory

short int i;


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Working with Pointers Declaring pointers (the referenced type):

int *p; /* points only to integers */

double *q; /* points only to doubles */

char *r; /* points only to characters */

Initializing pointersint i;

p = &i;

use the * (indirection) operator to access whatsstored in the objectprintf("%d\n", *p);




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Pointer Variables Addresses can be stored in specialpointer

variables.

When we store the address of a variable i in thepointer variable p, we say that p points to i.

A graphical representation:




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The Indirection Operator int i;

p = &i;

i = 1;

printf("%d\n", i); /* prints 1 */

printf("%d\n", *p); /* prints 1 */

*p = 2;

printf("%d\n", i); /* prints 2 */

printf("%d\n", *p); /* prints 2 */Copyright 2008 W. W. Norton & Company.



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Pointer Assignment Assume that the following declaration is in effect:int i, j, *p, *q;

Example of pointer assignment:p = &i;

Another example of pointer assignment:q = p;




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Pointer Assignment Ifp and q both point to i, we can change i by

assigning a new value to either*p or*q:

*p = 1;

*q = 2;


All rights reserved.

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Chapter 12

Pointers and Arrays


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Pointer Arithmetic Pointers can point to array elements:int a[10], *p;

p = &a[0];

we can store the value 5 in a[0] by writing*p = 5;



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Pointer Arithmetic Ifp points to an element of an array a, the other

elements ofa can be accessed by performingpointer arithmetic (oraddress arithmetic) on p.

C supports three forms of pointer arithmetic: Adding an integer to a pointer Subtracting an integer from a pointer Subtracting one pointer from another



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Adding an Integer to a PointerAssume the following declarations are in effect:

int a[10], *p, *q;

Then:

p = &a[2];

q = p + 3;

p += 6;



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Using an Array Name as a Pointer Pointer arithmetic is one way in which arrays and

pointers are related.

Another key relationship:The name of an array can be used as a pointer

to the first element in the array.

This relationship simplifies pointer arithmetic andmakes both arrays and pointers more versatile.



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Using an Array Name as a Pointer Suppose that a is declared as follows:int a[10];

Examples of using a as a pointer:*a = 7; /* stores 7 in a[0] */

*(a+1) = 12; /* stores 12 in a[1] */

In general, a+i is the same as &a[i]. Both represent a pointer to element i ofa.

Also, *(a+i) is equivalent to a[i]. Both represent element i itself.



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Example Programs Swap the values of two integers using pointers Find largest and smallest elements in an array Sum the elements of an array using pointers Process the rows of a multidimensional array

using pointers



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Chapter 13

Strings


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How String Literals Are Stored

The string literal "abc" is stored as an array offour characters:

The string "" is stored as a single null character:



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Initializing a String Variable

A string variable can be initialized at the sametime its declared:

char date1[8] = "June 14";

The compiler will automatically add a nullcharacter so that date1 can be used as a string:



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Character Arrays versus Character Pointers

Thanks to the close relationship between arraysand pointers, two ways to declare a string:

char date[] = "June 14";

char *date = "June 14";

In the array versiondate is an array name. the characters stored in date can be modified.

In the pointer versiondate is a pointer variable that can point to other strings.date points to a string literal that shouldnt be modified.



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Reading Strings Character by Character

read_line consists primarily of a loop that callsgetchar to read a character and then stores the character

in str, provided that theres room left:int read_line(char str[], int n)

{int ch, i = 0;

while ((ch = getchar()) != '\n')

if (i < n)

str[i++] = ch;

str[i] = '\0'; /* terminates string */return i; /* number of characters stored */}



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Accessing the Characters in a String

A function that counts the number of spaces in astring:

int count_spaces(const char s[])

{int count = 0, i;

for (i = 0; s[i] != '\0'; i++)

if (s[i] == ' ')

count++;return count;

}



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Accessing the Characters in a String

A version that uses pointer arithmetic instead ofarray subscripting :

int count_spaces(const char *s)

{int count = 0;

for (; *s != '\0'; s++)

if (*s == ' ')

count++;return count;

}



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Arrays of Strings: 2D array

charplanets[][8]={"Mercury","Venus","Earth",

"Mars","Jupiter","Saturn",

"Uranus","Neptune","Pluto"};



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Arrays of Strings: Ragged Array

char *planets[] = {"Mercury", "Venus, "Earth,

"Mars", "Jupiter", "Saturn,

"Uranus", "Neptune", "Pluto"};



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Command-Line Arguments

Access to command-line arguments in mainint main(int argc, char *argv[]){}

If the user enters the command line> ls -l remind.c

then argc will be 3, and argv will be:



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Using the C String Library

Programs that need string operations should contain thefollowing line:

#include

The C library provides a rich set of functions forperforming operations on strings.char *strcpy(char *s1, const char *s2);

size_t strlen(const char *s);

char *strcat(char *s1, const char *s2);int strcmp(const char *s1, const char *s2);



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Program Examples

Count the number of spaces in a string (usingarray or pointer)

Checking Planet Names Writing of String functions:

Searching for the End of a String Copying a String



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Chapter 16

Structures


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Declaring Structure Variables

A structure is a logical choice for storing acollection of related data items.

A declaration of two structure variables that storeinformation about parts in a warehouse:struct {

int number;

char name[NAME_LEN+1];

int on_hand;} part1, part2;



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Declaring Structure Variables

The members of a structure arestored in memory in the order in

which theyre declared.

Appearance ofpart1 Assumptions:

part1 is located at address 2000. Integers occupy four bytes.NAME_LEN has the value 25. There are no gaps between the

members.



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Initializing Structure Variables

A structure declaration may include an initializer:struct {

int number;


int on_hand;} part1 = {528, "Disk drive", 10},

part2 = {914, "Printer cable", 5};

Appearance ofpart1 after initialization:



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Operations on Structures

To access a member of a structure, we use . Statements that display the values ofpart1:

printf("Part number: %d\n", part1.number);

printf("Part name: %s\n", part1.name);printf("Quantity on hand: %d\n", part1.on_hand);

They can appear on the left side of an assignment:part1.number = 258;

part1.on_hand++;



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Declaring a Structure Tag

A structure tagis a name used to identify aparticular kind of structure.

The declaration of a structure tag named part:struct part {int number;


int on_hand;

};

The part tag can be used to declare variables:struct part part1, part2;



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Structures as Arguments and Return Values

A function that returns a part structure:struct part build_part(int number,

const char *name,

int on_hand)

{struct part p;

p.number = number;

strcpy(p.name, name);

p.on_hand = on_hand;

return p;}

A call ofbuild_part:part1 = build_part(528, "Disk drive", 10);



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Structures as Arguments and Return Values

A function with a structure argument:void print_part(struct part p)

{

printf("Part number: %d\n", p.number);

printf("Part name: %s\n", p.name);

printf("Quantity on hand: %d\n",p.on_hand);

}

A call ofprint_part:print_part(part1);



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Program Example

Maintaining a Parts Database (Inventory) Arrays of structuresNested structures Structures that include array members Functions that have structures as parameters Functions that return structures



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Chapter 17

Dynamic Memory Management


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Memory Allocation Functions

The header declares three memoryallocation functions:

mallocAllocates a block of memory but doesnt

initialize it.callocAllocates a block of memory and clears it.

reallocResizes a previously allocated block of

memory.

These functions return a value of type void* (ageneric pointer).

If a memory allocation function fails, it returns anull pointer.



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Using malloc to Allocate Memory for a String

A call ofmalloc that allocates memory for astring ofn characters:

char* p;

p = (char *) malloc(n + 1);



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Using malloc to Allocate Memory for an Array

Suppose a program needs an array ofn integers,where n is computed during program execution.

int *a;

a = malloc(n * sizeof(int));

Or

a = calloc(n, sizeof(int));



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Deallocating memory

Memory leak and garbage collector Deallocating memory using free:void free(void *ptr);

The Dangling Pointer Problem


All i ht d

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