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Table of Contents
- Headers #include<___.h>.....................................................................
- Lecture 2.....................................................................................
- Conversion Specifiers – printf & scanf...................................................
- Steps in C Compilation.........................................................................
- Lecture 4.....................................................................................
- Types..................................................................................................
- Capacity.............................................................................................
- Literal Values......................................................................................
- Boolean Type: _Bool.............................................................................
- Operators & Precedence......................................................................
- Arithmetic Conversion 5 Rules.............................................................
- Lecture 5.....................................................................................
- Flow of Control....................................................................................
- Storage Class......................................................................................
- Functions............................................................................................
- Multi-File Programs.............................................................................
- Lecture 6...................................................................................
- Arrays...............................................................................................
- Strings..............................................................................................
- Lecture 7...................................................................................
- Multi-Dimensional Arrays...................................................................
- Executing C Programs........................................................................
- Lecture 8...................................................................................
- Lecture 9...................................................................................
Models of Programming Imperative Object-oriented Procedural Static Typing Dynamic Typing GCC gcc -Wall -std=c99 -g myProgram.c -o myProgram
Headers #include<___.h>
stdlib.h – standard library o EXIT_SUCCESS (0), EXIT_FAILURE (8) stdio.h – standard i/o header o int getchar(void) : returns code for the next character read (int 0 to 255) or -1 for EOF if no more input o int putchar(int c); Sends one char to the terminal Returns character written or EOF if unable to send o printf – generates formatted output printf(“value:%6.2f\n”, 3.1415926); 6 = field width: take at least 6 characters to print it .2 = precision: round output to 2 digits o scanf - Reads formatted input scanf(“&d”, val); pass-by-value (doesn’t change the variable, passes a copy) scanf(“&d”, &val); pass-by-reference (changes what’s in the variable val) int matches = scanf(“%f%d”, &floatVal, &intVal); matches = 2 if both float and int vals matched 1 if only 1 matched 0 if no value matched -1 if end-of-file reached before matching Input: 37.22b5 would match 37.22 to floatVal, and return 1 ctype.h o bool isalpha(int ch); Check if a character is a letter o bool isspace(int ch); Check if character is whitespace o bool isdigit(int ch); Check if character is a digit o bool isprint(int ch); Check if character is printable (not a control character) o Others: isalnum(int ch); [is alphabet/number] o ispunct(int ch); isupper(int ch); o toupper(int ch); Converts lower to upper case
\’ Single quote \” Double quote \ Backslash \n Newline \t Horizontal tab
Conversion Specifiers – printf & scanf
Format Specifier Input/Output %c Single character (given its numeric character code) %d Decimal integer %ld long integer %f float or double %s String %p Pointers (in hexadecimal) %zd size_t or sizeof() %o Integer in octal %x Integer in hexadecimal %X Integer in hexadecimal (capialized) %u Unsigned integer %lli long long int (decimal or any of the formats above). User can pick what base to use.
Steps in C Compilation
Source Code (Preprocessing) Expanded Source Code (Lexical Analysis (tokenization)) Tokens (Parsing) Parse Tree (Code Generation) Assembly Code (Assembling) Object Code More Objects Libraries (Linking) Executable
Lecture 4
bit = smallest unit of computer information byte = 8 bits, single character of text
Types
Floating Point Types: long double, double, float Integer Types (signed & unsigned): long long, long, int, short, char Types Smaller than integers: _Bool, void Naming: o Signed is usually the default so is left off (ex: signed int = int) o Int is optional for short, long ,and long long (ex: long int = long) Signed: positive & negative values o Usually the default Unsigned: 0 and positive values
Capacity
Range of type is platform dependent. Can look in the /usr/include/limits.h header to find out how much memory is used for each variable type. #include for constants: SHRT_MIN, SHRT_MAX, USHRT_MAX, INT_MIN, INT_MAX, UINT_MAX, LONG_MIN, LONG_MAX (signed range), ULONG_MAX(unsigned range) Integers Type Bit s Byte s Signed Unsigned char 8 1 -128 to 127 0 to 255 short 16 2 -32,768 to 32,767 0 to 65, int 32 4 -2,147,483,648 to 2,147,483, 0 to 4,294,967, long 64 8 - 9,233,372,036,854,775, 808 to 0 to 18,446,744,073,709, ,
! Logical not (type) Type cast: (destination_type) expression Explicitly specifies the type (as opposed to implicit type casting) Ex: c = (unsigned char) d; Can even cast to void to throw away result: (void) f(x); sizeof tells you how much memory it takes to store something size_t sizeType = sizeof(x); printf(“%zd\n”, sizeType);
- / % Multiply, divide, mod
- Add, subtract < <= > >= Relational operators == != Equals, not equals && Logical and || Logical or ?: Ternary operator: test? expr1 : expr Same as if (test){expr1} else {expr2} Ex: c = a>b? a: b; = += -= *= … Assignment, and its friends , Comma operator: Chain together multiple expressions. Expressions get evaluated left to right
Arithmetic Conversion 5 Rules
- If an operand is a floating point type, convert to the wider floating point type
- If either operand rank is lower than int (_Bool, char, short), convert to at least the rank of int o Lower ranks are promoted to signed int if it is large enough to hold all values
- If both types have the same “signed-ness”, promote to the higher- ranked type
- If the signed type can store every value the unsigned type can, convert to the signed type
- If the signed type isn’t large enough, use the unsigned version of the higher-ranked type o Given 2 equal ranked types of different signed-ness, C will use the unsigned type o Ex: unsigned int x = 999; x > -1 would be false b/c -1 would be converted to an unsigned value which would overflow to a very positive value Function parameters : Parameter values get converted to the parameter types expected by the function Return value gets converted to the return type
Lecture 5
Constant expressions: expression that always produces the same result o int three = 3;
Flow of Control
switch case o switch (val ) { case 0: val +=1; break case 2/2: val -=1; break; case 25/7%2 + 19 -6*3: val *=2; break; Default: … } break: Cancel the innermost loop early continue: Skips the rest of the innermost loop’s current iteration goto: Can jump to a label as long as it’s in the same function o for (int i = 0; i < 0; i++) { if (i > 12) { goto done; } } done: … Expression Evaluation Order Sequence points: Places where the order of evaluation are well defined; and the known side effects to the left will occur before evaluation continues o ; Statement termination o ) Closing parenthesis in a condition evaluation o Operators: a && b a || b a? b: c a , b (but not between function parameters)
Storage Class
Global Variables : Static Storage Class (Statically-Allocated Data) C Program Memory Executable Increasing Addresses Machine Code Statically- Allocated Data (global vars) Heap Data
Compilation Unit : C source code that is compiled and treated as 1 logical unit. Declarations and definitions within a compilation unit determine the scope of functions and data objects. Build multiple files: gcc -Wall -std=c99 -g tournament.c game.c summary.c tournament Linker: Take 1 or more object files generated by the compiler and combines them into 1 executable program. Connects each use with its memory location Header File : Advertises the public interface for an implementation file o Javadoc comments go here o Ex: helper.h (header file) extern int x; void f(int); helper.c (implementation file) #include “helper.h” int x = 5; void f( int a ){…} main.c #include “helper.h” // so it can use functions in helper.c Helper.h and helper.c make a component together Implementation File: File with the implementation of operations specified in the header file
bytes each type takes
Lecture 6
Arrays
Initialize : o int a[10]; a[0] = 1; // sets value one at a time printf(“%d”, 0[a]); -> “1” // Can access 0 this way too o int a[] = {7, 14, 21, 28}; //compiler figures out size o int a[5] = {7, 14, 21}; // Partial initialization o int a[] = { 1, [7]=10, 90, [2]=40, 2, [5]=35 }; Partial initialization, unspecified index set to 0. Stack-allocated array o Contains garbage if not initialized o Variable-length array: Size when initializing can be determined during execution int main(void) { int n; printf(“How many values would you like: “); scanf(%d”, &n); int list[n]; … } Aren’t resizable but can choose a different size every time the variable goes into scope Can’t use initialization syntax for variable-length arrays: int a[n] = {7, 14, 21}; int a[n] = { }; Statically-allocated array o Contains zeros if not initialized o Size must be a constant expression: int sequence[100]; int main(){…} Functio n Description Example sizeof() Reports the size of its argument. Can be used to figure out array length in some cases. int a; size_t aSize = sizeof(a);\4 bytes float b[100]; …
dest[], char src[]) null terminator strncpy(char dest[], char src[], size_t n) Copy strings with a limit to the number of characters written to the destination. If short, pads with zeros up to n. Won’t null terminate if no room strcmp( char s1[], char s2[] ) Compares strings < 0 if s1 is before s 0 if equal (true) > 0 if s1 is after s strncmp(s1, s2, size_t n) Compares at most n characters strcat(char dest[], char src[]) Copies string from source to the end of dest Dest must be initialized, can be empty strncat(dest, src, n) Gives a bound on the length of the string appended and adds \0 at end. Helps ensure null terminator is added. atoi() (^) Parse string as int int atoi(char str[]) atof() (^) Parse strings as doubles double atof(char str[]) atol() (^) Parse strings as long ints long atoll(char str[]) atoll() (^) Parse strings as long long ints long long atoll(char str[])
Lecture 7
Multi-Dimensional Arrays
int table[# rows][# cols] Initialization (partial can be done & unspecified will be filled with zeros): o int table[3][4]={ {0, 1}, (16, 25, 36, 49}, {64}
o int table[ ][4] = { [1]={16, 25, 36, 49}, [0] ={[1] = 1}, [2][0] = 64 }; o # of rows can be left blank and the compiler can determine the size o Inner dimensions must be specified sizeof o sizeof(table) = size of whole array o sizeof(table[0]) = size of row o sizeof(table[0][0]) = size of an element Multi-dimensional arrays as parameter: o Int process(short block[][7][10]) o Must specify array length as a parameter too if want to use it: void sumTable(int rows, int cols, int table[][cols]){}
Executing C Programs
Compiled code: C, Interpreted Code: Java
Lecture 8
Pointer Operators & : Address-of operator o &a : address of variable a * : Type operator, creates new types o type * identifier;
