Research Tools & Techniques

Transcription

1 Research Tools & Techniques for Computer Engineering Ron Sass rsass University of North Carolina at Charlotte Fall / 106

2 Review of C L02: Part I data types operators control structures L03: Part II data structures pointer arithmetic compiler flow 17/ 106

3 C: An Imperative Language uses byte-addressable memory model machine state is stored in a linear array of memory cells each memory cell is exactly one byte (8 bits) each memory cell has an address uses imperative programming model: execution is a command-response cycle : byte : : FFFFFFFF:. 18/ 106

4 Data Types (32-bit machines) Types char int float Special void pointers: * addresses: & Modified Types unsigned char unsigned int short int short long int long long double long double no Boolean types ( ) no Strings! ( ) typedef existing-type new-type ; 19/ 106

5 Variable Declarations with Data Types location is determined by how/where the variable is declared divided into sections text data stack bss others : text data bss FFFFFFFF: stack 20/ 106

6 Variable Declarations (cont d) variables have lifetime scope variables must start with an letter or underscore and then can consist of letters, digits, or underscores variables are case sensitive 21/ 106

7 Variable Examples Valid int xcoord ; int y_coord ; char _code ; double len ; Invalid xcoord : int ; int 1coord ; double char _code ; 22/ 106

8 Expressions combine variables, constants with operators binary operators + / (no e x ; use math library) & ˆ bit-wise OR, AND, XOR < <= == >= > comparisons && Boolean OR, AND unary operators negate sizeof num. of bytes bitwise not & address of dereference pointer [] dereference an array tri-operators cond?x : y expression evaluates x if cond else y 23/ 106

9 Assignment Statements all statements must be inside of a function declare variables before using them syntax: <lhs> = <rhs> ; where 24/ 106

10 First C Example create a function that that computes f (x, y) = 1 x 2 + y 2 double func ( double x, double y ) { double denom, frac ; denom = x*x + y*y ; frac = 1.0/denom ; } return frac ; 25/ 106

11 Input/Output Input and Output are not part of the syntax of the language accomplished with library calls #include <headname> add -llibname to compiler 26/ 106

12 Output: printf printf is a function that takes a format string zero or more variables to be formatted formatted string is displayed on screen use man 3 printf to find all convertions and options d x X f c s (integer) decimal (integer) hexadecimal (integer) hexadecimal (in caps) float or double char string 27/ 106

13 Printf Examples Example printf("%d\n",12) ; 12 printf("%5d\n",13) ; 13 printf("%05d\n",13) ; printf("%x\n",13) ; c printf("%x\n",13) ; D printf("%f\n",3.1245) ; printf("%6.3f\n",13) ; Output 28/ 106

14 Printf Examples (2) Example: printf("the number %d is magic.\n",123) ; Output: The number 123 is magic. Example: float x,y,z ; x = 3.2 ; y = 6.4 ; z = x * y ; printf("the product of %f and %f is %f\n",x,y,z) ; Output: The product of and is / 106

15 Input: scanf scanf is a function that takes an input format string zero or more variables to be read from keyboard use man 3 scanf to find all convertions and options d f lf c (integer) decimal float double char 30/ 106

16 Scanf Examples Assuming i, i1, i2 are declared int, f is declared float, and d is declared double, then... Example Action scanf("%d\n",&i) ; reads one int s per line printf("%d%d\n",&i1,&i2); reads two int s per line printf("%f\n",&f) ; reads a float printf("%lf\n",&d) ; reads a double 31/ 106

17 Control Structures assignment statements by themselves are not very useful imperative model has three control structures that allow statements to be combined sequence and then do that) conditional any two statements can be joined (do this any two statements can be joined as alternatives (do this or that but not both) iterative any statement can be done repetitively (do this until some condition is met) moreover, each of these constructs are statements themselves programming means recursively combining statements together to create meet functionality 32/ 106

18 C Control Structures sequence: starts with a { and ends with a }, statements executed in order (left-to-right, top-to-bottom) conditional if/then/else switch statement tri-operator repetive for while do/until 33/ 106

19 While Loop where while ( cond ) { statement } cond is an integer expression statement is (possibly recursive) statement 34/ 106

20 For Loop short-cut for common while loop structure for ( init, cond, post ) { statement } } init while ( cond ) { statement post } 35/ 106

21 If/Then/Else where if ( cond ) { statement1 } else { statement1 } cond is an integer expression statement1 is (possibly recursive) statement statement2 is (possibly recursive) statement 36/ 106

22 The Main Function int main ( int argc, char *argv[] ) { }. return integer 37/ 106

23 Live Demo 38/ 106