Multidimension array, array of strings

Transcription

1 1 Multidimension array, array of strings char messages[3][7] ={ Hello, Hi, There ; Array of strings H e l l o \0 H i \0 T h e r e \0 Each row (e.g., message[0]) is a char array (string) 1 messages [0] Hello printf( %s, messages[0]); messages [1] Hi printf( %c, messages[2][1]); messages [2] There arrays: set /get in general char message[3][7]; strcpy(message[0], hello ) message[0][2] = L ; H e l l o \0 H i \0 T h e r e \0 sprintf(message, %s there!, hi ); hi ther sprintf(message[1], %s %d %.0f, j, 1, 2.3); sscanf(message[1], %s %d %f, name, &age, &wage ) tokenizing the string fgets(message[2], 7, stdin) fputs(messge[2], stdout) 2

2 2 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions Last week Pointer arithmetic Pointers and arrays (5.3) Arrays of pointers Command line argument Pointer to arrays and two dimensional arrays Pointer to functions Pointer to structures Memory allocation Later: file IO Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) Stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) p1-p2 p1<>!= p2 Array as function argument decay Pass sub_array Arrays of pointers Command line argument Pointer to arrays and two dimensional arrays Pointer to functions Pointer to structures Memory allocation file IO Last week

3 3 Some example of Pointers int *p1, *p2, x = 8, y = 9; p1 = &x; p2 = &y; x = y Precedence p53 Operator Type Operator Associativity Primary Expression Operators Unary Operators Binary Operators () []. -> left-to-right * & + -! ~ (typecast) sizeof * / % arithmetic + - arithmetic >> << bitwise < > <= >= relational ==!= relational & ^ bitwise bitwise bitwise && logical logical right-to-left left-to-right Ternary Operator?: right-to-left Assignment Operators = += -= *= /= %= >>= <<= &= ^= = right-to-left Comma, left-to-right ptr = &x; *x = 5; No () needed

4 4 ++ * ptr * ptr; * ptr = * ptr + 1 * ++ ptr ptr = ptr +1; *ptr; (* ptr) ++ * ptr; * ptr = * ptr + 1 * ptr ++ * ptr; ptr = ptr +1 7 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions Pointer arithmetic Pointers and arrays Arrays of pointers Command line argument Pointer to arrays and two dimensional arrays Pointer to functions Pointer to structures Memory allocation Later: file IO

5 5 Pointer to pointers another example int x = 12; int *ptr; ptr = &x; ptr_to_ptr 1006 ptr int **ptr-to-ptr /* I am a pointer to pointer */ ptr-to-ptr = &ptr; /* points to ptr */ **ptr-to-ptr = 20; /* multiple indirection*/ valid operations x, &x *x x ptr, &ptr, *ptr, **ptr ptr-to-ptr, &ptr_to_ptr *ptr-to-ptr, 9 ** prt-to-ptr, Multiple indirection d * 1006 * * c b 1000 a Consider the following code: int a = 3; int *b = &a; int **c = &b; int ***d = &c; Here are how the values of these pointers equate to each other: *d == c; **d == *c == b; ***d == **c == *b == a == 3; 10

6 6 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions Pointer arithmetic Pointers and arrays Arrays of pointers Command line argument Pointer to arrays and two dimensional arrays Pointer to functions Pointer to structures Memory allocation Later: file IO Pointers and function arguments In C, all functions are called by value Value of the arguments are passed to functions, but not the arguments themselves (i.e., not call by reference) two questions 1. How to pass a structure such as array? 2. How to modify the argument? Tackle the swap() problem How to return structure, and/or more than one values Passing structure and modify by passing addresses/pointers Efficient. Input / output Possibly modify passed arguments strcpy (char[] dest, char[] source) 12 strcpy (char * dest, char * source)

7 7 Mr. Main: Hi, Binding function, I have some manuscripts, stored in lockers (memory), and I want you to bind them into a book. Could I bring the manuscripts to you? main Ms function: Hi, Mr Main, here is how we work: First, we don t take your original manuscript (not call by reference). We always photocopy things (call by value), and work on copies. Second, we only photocopy one paper a time(a single value) Mr. Main: Then, is there a way to have my original manuscripts bound by you? Mr. Main: Hi, Mrs binding function, I have some manuscripts, stored in lockers (memory), and I need you to bind them into a book. Could I bring the manuscripts to you? main Ms function: Hi, Mr Main, here is how we work: Firstly, we don t take your original manuscript (not call by reference). We always photocopy things (call by value), and work on copies. Secondly, we only photocopy one paper a time(a single value) Mr. Main: Then, is there a way to have my original papers bound by you? Ms function: Write down the locker number (address) on a paper, bring that paper to us (pass pointer/address) we photocopy the paper (still call by value), Then, based on the locker number on the copy, we go to your locker, fetch your original manuscripts there and bind them! Mr. Main: Cool!

8 8 The Correct Version I am expecting int pointers void swap(int *px, int *py) { int temp; temp = *px; *px = *py; *py = temp; px = &a; py = &b Call by value px = &a; py = &b; void main( ) { int a=2, b=40; swap(&a, &b); 15 printf( %d %d, a, b); The Correct Version I am expecting int pointers void swap(int *px, int *py) { int temp; temp = *px; *px = *py; *py = temp; px = pa = &a; py = pb = &b Call by value px = pa = &a; py = pb = &b; void main( ) { int a=2, b=40; int *pa=&a; int *pb=&b; swap(pa,pb); printf( %d %d, a, b); 16 The other way to pass address

9 9 Now understand scanf() -- more or less int x=1; int y = 2; swap(&x,&y); int x; scanf ( %d, &x); printf( %d,x); int x; int *px = &x; scanf( %d, px); printf( %d,*px); But why array name is used directly scanf ( %s, arrname) scanf ( %d %s, &x, arrname) 17 scanf( %d, &px);? // store input value into px, not x Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions Pointer arithmetic Pointers and arrays Arrays of pointers Command line argument Pointer to arrays and two dimensional arrays Pointer to functions Pointer to structures Memory allocation Later: file IO

10 10 Pointers and variable type base type is important! oo c sh i int* pi = &i; char *pc=&c; short *psh=&sh; Each point store the address of the first byte of its pointee How many bytes to transfer? Base type is important! Allowing proper read/write. y = *pi; *pi = 100; r/w 4 bytes from 96 [96,97,98,99] c = *pc; *pc= d ; r/w 1 byte from 91 s=*psh; *psh=2; r/w 2 bytes from 93 [93, 94] 19 Pointer arithmetic pi pi oo c sh i Limited math on a pointer Four arithmetic operators that can be applied Result is a pointer (address) int* pi=&i; char * pc=&c; short * psh=&sh; 20 pi + 1? address =100 psh + 2? address = 97. pi++? pc++? psh++? pi = pc = psh =

11 11 Pointer arithmetic Incrementing / decrementing a pointer by n moves it ahead n units p ± n unit Size of a unit is based upon the size of the type If p points to an integer of 4 bytes, p + n advances by 4*n bytes: p + 2 = *2 = 104 p - 1 = 96 4 = 92 p p+1 p *p *(p+1) *(p+2) 21 How would we need to move pointer? Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions Pointer arithmetic Pointers and arrays (5.3) Arrays of pointers Command line argument Pointer to arrays and two dimensional arrays Pointer to functions Pointer to structures Memory allocation Later: file IO

12 12 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) How arrays are stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) Array as function argument decay Pass sub_array Later: file IO Pointers and Arrays (5.3) Array members are next to each other in memory arr[0] occupies in the lowest address e.g. int arr[3]; arr[0] arr[1] arr[2] short 24

13 13 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) Stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) Array as function argument decay Pass sub_array Later: file IO Pointers and Arrays (5.3) Array members are next to each other in memory arr [0] occupies in the lowest address ptr e.g. if x is an integer ptr+1 array int x[3]; ptr arr[0] arr[1] arr[2] int arr[3]; int *ptr; ptr = &arr[0]; /* 92 */ ptr + 1?; /* 96 &arr[1] */ ptr + 2?; /* 100 ptr = &arr[2] */ *(ptr +2 ) =. /* *&arr[2] arr[2] */ ptr + i == & arr[i] *(ptr + i) == arr[i]

14 14 Sum of an int array #define N 10 int a[n], sum, i; sum = 0; for (i=0; i<n; i++) sum += a[i]; #define N 10 int a[n], sum, i,*p; p = &a[0]; sum = 0; for (i=0; i< N; i++) sum += *(p + i); #define N 10 int a[n], sum, i,*p; p = &a[0]; sum = 0; for (i=0; i< N; i++){ sum += *p; p++; 27 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) Stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) Array as function argument decay Pass sub_array Later: file IO

15 15 Pointers and Arrays (5.3) There is special relationship between pointers and arrays when you use array, you are using pointers! int i, arr[20], char c; scanf( %d %c %s, &i, &c, arr); /* &arr is wrong */ Identifier (name) of an array is equivalent to the address of its 1 st element. arr == &arr[0] arr + 1 == address of next element == &arr[1] *(arr + 2) == *(&arr[2]) == arr[2] int arr[20]; int * p; ptr = arr; /* == (ptr = &arr[0]) */ ptr + 8 == & arr[8] *(ptr + 8) == arr[8] 29 Pass (copy) to a function (arr) -- the address of arr[0] Pointers and Arrays (5.3) There is special relationship between pointers and arrays Identifier (name) of an array is equivalent to the address of its 1 st element. arr == &arr[0] int arr[20]; int * p; ptr = arr; /* ptr = &arr[0] */ arr[4] *(ptr + 4) *(arr + 4) equivalent 30 ptr[4] Pass (copy) to a function (arr) -- the address of arr[0]

16 16 Sum of an int array #define N 10 int a[n], sum, i; sum = 0; for (i=0; i<n; i++) sum += a[i]; #define N 10 int a[n], sum, i,*p; p = a; /* p=&a[0] */ sum = 0; for (i=0; i< N; i++) sum += *(p + i); 31 #define N 10 int a[n], sum, i,*p; p = a /* p=&a[0] */ sum = 0; for (i=0; i< N; i++) { sum += *p; p++; Array name is not pointer! int arr[20]; int * p = arr; p and arr are equivalent and they have the same properties: &arr[0] Difference is that arr is a string constant we could assign another value to the pointer p arr will always point to the first of the 20 integer numbers of type int. 32 p = arr; /*valid*/ arr = p; /*invalid*/ p++; /*valid*/ arr++; /*invalid*/ arr = hi ; /*invalid*/ arr + 2 /* valid */

17 17 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) Stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) Array as function argument decay Pass sub_array Later: file IO Pointer arithmetic (revisit) +n -n result is an new address/pointer If p1, p2 points to different elements of the same array Differencing: p1 p2 how far apart the elements are Comparison : ==!= > < >= <= p1 < p2 is true (1) if p1 points to earlier elements than p2 is false (0) otherwsie p1 p2 34

18 18 Pointer arithmetic on arrays (revisit) Adding an Integer to a Pointer Assume that the following declarations are in effect: int a[10], *p, *q, i; Example of pointer addition: p = &a[2]; q = p + 3; p += 6; Assume int array. p= &a[2] = 96 Then q = =108 = &a[5] Pointer arithmetic on arrays (revisit) Subtracting an Integer from a Pointer If p points to a[i], then p - j points to a[i-j]. Example: p = &a[8]; q = p - 3; Assume int array. p= &a[8] = 120 Then q = =108 = &a[5] p -= 6;

19 19 Pointer arithmetic on arrays (revisit) Subtracting One Pointer from Another When one pointer is subtracted from another, the result is the distance (measured in array elements) between the pointers. If p points to a[i] and q points to a[j], 7 then p - q is equal to i - j. p = &a[5]; // 108 q = &a[1]; // i = p - q; /* i is 4 (108-92)/4 = 4 */ i = q - p; /* i is -4 */ 37 Pointer arithmetic on arrays (revisit) Comparing Pointers Pointers can be compared using the relational operators (<, <=, >, >=) and the equality operators (== and!=). Using relational operators is meaningful only for pointers to elements of the same array. The outcome of the comparison depends on the relative positions of the two elements in the array. 38 p = &a[5]; q = &a[1]; p <= q is 0 false p >= q is 1. true

20 20 Sum of an int array #define N 10 int a[n], sum, i; sum = 0; for (i=0; i<n; i++) sum += a[i]; #define N 10 int a[n], sum, i,*p; p = a; /* p=&a[0] */ sum = 0; for (i=0; i< N; i++) sum += *(p + i); 39 #define N 10 int a[n], sum, i,*p; p = a; /* p=&a[0] */ sum = 0; for( i=0;i< N; i++) { sum += *p; p++; #define N 10 int a[n], sum, i,*p; p = a; /* p=&a[0] */ sum = 0; while( p < a+n ) { sum += *p; p++; Summary of pointer arithmetic Legal: assignment of pointers of the same type p2 = p1 adding or subtracting a pointer with an integer p++, p+2, p-2 subtracting or comparing two pointers to members of the same array p2- p1, if (p1 < p2) if (p1 == p2) assigning or comparing to zero (NULL) p = NULL p==null Illegal: p1+p2; p1*p2; p1*3 add two pointers, multiply or divide two pointers, integers shift or mask pointer variables p >> 3 add float or double to pointers p assign a pointer of one type to a pointer of another type (except for void *) without a cast 40

21 21 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) Stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) p1-p2 p1<>!= p2 Array as function argument decay New Pass sub_array today Arrays of pointers Command line argument Pointer to arrays and two dimensional arrays Pointer to functions Pointer to structures Memory allocation file IO Review Last lecture Arrays Passed to a Function Arrays passed to a function are passed by starting addresses. The name/identifier of the array passed is treated as a pointer to its first element. arr = &arr[0]; Thus, function expecting a char array can be declared as either strlen(char s[]); or strlen(char * s); Actual prototype man 3 strlen The call to this function does not copy the array in the function call, just a address (starting address -- a single value) to it. char a[20] = Hello ; char * ps = a; strlen(a); /* strlen(&a[0]) */ decay 42 strlen(ps); scanf( %s, a); scanf( %s, ps); Pass by value: s = a = &a[0] s = ps = a = &a[0] printf( %s, ps);

22 22 Arrays Passed to a Function Arrays passed to a function are passed by starting address. The name/identifier of the array passed is treated as a pointer to its first element. arr = &arr[0]; Thus, function expecting a char array can be declared as either strcpy(char A[], char B[]); or strcpy(char * pa, char * pb); Actual prototype man 3 The call to this function does not copy the array in the function call, just a pointer (starting address -- a single value) to it: char a[20]; char b[20] = hi ; char * ptra = a; char * ptrb = b; decay 43 strcpy(a, b) /* copy_array(&a[0], &b[0])*/ strcpy(ptra, ptrb); printf ( %s %s, ptra, b) Arrays Passed to a Function Arrays passed to a function are passed by starting address. The name/identifier of the array passed is treated as a pointer to its first element. arr = &arr[0]; By passing an array by a pointer 1. Array can be passed (efficiently) 2. Argument array can be modified decay 44

23 23 Computing String Lengths /* strlen: return length of string s */ int strlen(char *s) /* or (char s[]) */ { Examples using prior knowledge int n=0; while ( *(s+n)!= '\0') { n++; return n; Function does not know/care if it an array or not int strlen(char s[]) { int n=0; while ( s[n]!= '\0') { n++; return n; Callers: strcpy(arr, "hello, world"); /* string constant */ char * ptr = arr; strlen(arr); 45 /* char array; */ strlen(ptr); /* char *ptr; */ Computing String Lengths -- another version /* move the pointer s */ int strlen(char *s) /* or (char s[]) */ { Examples using prior knowledge int n =0; while (*s!= '\0 ) { s++; n++; return n; Function does not know/care if it an array or not int strlen(char s[]) { int n; for(n=0; s[n]!= '\0 ; n++) ; return n; Callers: strcpy(arr, "hello, world"); /* string constant */ char * p = arr; strlen(arr); /* char array; */ s=arr strlen(ptr); 46 /* char *ptr; */ s=prt=arr

24 24 Examples using prior knowledge Computing String Lengths -- cool version Don t need n /* strlen: return length of string s */ int strlen(char *s) /* or (char s[]) */ { char *p = s; while ( *p!= \0 ) p++; return p - s; // how far are they apart? Callers: strcpy(arr, "hello, world"); /* string constant */ char * p = arr; strlen(arr); /* char array[100]; */ strlen(ptr); 47 /* char *ptr; */ Examples using prior knowledge Computing String Lengths -- cool version Don t need n /* strlen: return length of string s */ int strlen(char *s) /* or (char s[]) */ { char *p = s; while ( *s!= \0 ) s++; return s - p; // how far are they apart? Callers: strcpy(arr, "hello, world"); /* string constant */ char * p = arr; strlen(arr); /* char array[100]; */ strlen(ptr); 48 /* char *ptr; */

25 25 copy two strings Function does not know/care if it an array or not /* strcpy: copy two strings */ void strcpy(char *dest, char *src) /* or (char s[]) */ { while (1){ *dest = *src; if (*src = \0 ) *(dest+i)=*(src+i) return; src ++; dest ++; void strcpy(char *dest, char *src) { while ( (*src = *dest)!= \0 ) { src++; dest++; 49 int main(){ char aa [] = "23544"; int siz = sizeof(aa) / sizeof(char) -1; printf("size: %u\n", siz); /* 6/1-1 = 5 */ a = my_atoi(aa); /* convert an array of digit characters into a decimal int */ int my_atoi (char c[]){ int u = sizeof(c) / sizeof(char) -1; /* 8/1-1=7 */ while ( u >= 0 ). 50

26 26 Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) Stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) Array as function argument decay Pass sub_array Later: file IO Passing Sub-arrays to Functions It is possible to pass part of an array to a function, by passing a pointer to the beginning of the sub-array. my_func( int ar[ ] ) {... or my_func( int *ar ) {... caller my_func(&a[5]) or my_func(a + 5) 52

27 27 Passing Sub-arrays to Functions It is possible to pass part of an array to a function, by passing a pointer to the beginning of the sub-array. char arr[20] = hi world ; char * pa = arr; strlen (&arr[4]); strlen (arr + 4); strlen (pa + 4); 4 &arr[4] arr + 4 arr pa h i w o r l d \o 53 pa subarray Passing Subarrays to Functions -- Recursion int length (String s) // Java if (s contains no letter) return 0; return 1 + length(substring(s,1)); length( ABCD ) = 1 + length( BCD ) = 1 + ( 1 + length( CD )) = 1 + ( 1 + ( 1 + length( D ))) = 1 + ( 1 + ( 1 + (1+ (1+length( ) ))) 54 = 1 + ( 1 + ( 1 + (1+ (1+0) ))) = 4

28 28 Passing Subarrays to Functions -- Recursion int length (String s) // Java if (s contains no letter) return 0; return 1 + length(substring(s,1)); length( ABCD ) = 1 + length( BCD ) = 1 + ( 1 + length( CD )) = 1 + ( 1 + ( 1 + length( D ))) = 1 + ( 1 + ( 1 + (1+ (1+length( )))) = 1 + ( 1 + ( 1 + (1+ (1+0) ))) = 4 55 Array Arguments (Summary) The fact that an array argument is treated as a pointer has some important consequences. decay Consequence 1: Due to pass by value, when an ordinary variable is passed to a function, its value is copied; any changes to the corresponding parameter don t affect the variable. In contrast, by passing array by pointer, argument array can be modified 56 strcpy (message, hello ); scanf ( %s, message);

29 29 Pointers and arrays (Summary) Consequence 2: The time required to pass an array to a function doesn t depend on the size of the array. There s no penalty for passing a large array, since no copy of the array is made. Consequence 3: An array parameter can be declared as a pointer if desired. strlen (char * s) 57 Consequence 4: A function with an array parameter can be passed an array slice substring strlen (&a[6]), strlen(a + 6) General array as function argument Pass an array / string by only the address / pointer of the first element strlen( Hello ); decay You need to take care of how long it is, the function does not know if it is an array or just a pointer to char/int Two possible approaches: 1. Special token at the end (case of string ) 2. Pass the length as another parameter Function: arraylen(int *) arraysum(int *) 58 Caller: int a[20]; arrlen(a); arraysum(a);

30 30 strlen(char *) arraylen(int *, int n) Mr. Main: Hi, Mrs binding function, I have some manuscripts, stored in lockers (memory), and I need you to bind them into a book. Could I bring the manuscripts to you? main Ms function: Hi, Mr Main, here is how we work: First, we don t take your original manuscript (not pass by reference). We always photocopy things (call by value), and work on copies. Second, we only photocopy one paper a time(a single value) Mr. Main: Then, is there a way to have my original papers bound by you? Ms function: Well, then you also need to tell us where to stop fetching. Either 1) tell us how many lockers to fetch, or, 2) put a special token in the last locker Ms function: Write down the locker number (starting address) on a paper, bring that paper to us (pass pointer/address) we photocopy the paper (still pass by value), Then, based on the locker number on the copy, we go to your locker, fetch your original manuscripts there and bind them! Mr. Main: My manuscripts are in multiple (consecutive) lockers Pointers K&R Ch 5 Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) Stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) p1-p2 p1<>!= p2 Array as function argument decay Pass sub_array Arrays of pointers Command line argument Pointer to arrays and two dimensional arrays Pointer to functions Pointer to structures Memory allocation file IO

31 31 Written midterm next week in class Midterm page on course website 61 K&R Ch.2,4 Types and sizes Basic types, their size and constant values (literals) char: x >= a && x <= z ; x >= 0 && x <= 9 x>48 && x<=57 int: 122, 0122, 0x12F convert between different bases not good Arrays (one dimension) and strings (Ch1.6,1.9) hello has size 6 byes, length 5 h e l l o \0 Expressions Basic operators (math, relational and logical) %, y=x++; y=++x; if (i =2) Type conversion and promotion 9/2* *9/2 int i= 3.4 Other operators (bitwise, bit shifting, compound assignment, conditional) Bit:, &, ~, ^, << >> Compound: x += 10; x >>= 10; x += y + 3 Precedence of operators Functions and Program Structure (Chapter 4)

32 32 K&R Ch 4 C program structure Functions call by value swap() Categories, scope and life time of variables (and functions) Global vs. local variable, Scope, life time, initialization static C Preprocessing #include, #define SQUARE (x) (x)*(x) FILE LINE 63 K&R Ch 4, Appendix B Other C materials before pointer Common library functions [Appendix of K&R] 2D array, string manipulations o sscanf,sprintf, o fgets, fputs 64

33 33 K&R Ch 5 Pointers Basics: Declaration and assignment Pointer to Pointer Pointer and functions (pass pointer by value) Pointer arithmetic Pointers and arrays (5.3) Stored consecutively Pointer to array elements p + i = &a[i] *(p+i) = a[i] Array name contains address of 1 st element a = &a[0] Pointer arithmetic on array (extension) p1-p2 p1<>!= p2 Array as function argument decay Pass sub_array