CSC Programming for Science Lecture 8: Character Functions

Today’s Goal At the end of today’s lecture, you should know a number of character functions  These are useful when handling data files  They can also be used to make fun programs

Functions C includes many pre-defined functions  Just routines that do useful work  #include statement allow us to use functions Differs from what function means in math  printf & scanf do not return values  All of the math function do, however

#include Statements Listed at start of program  #include -- for math functions  #include -- for printf & scanf  #include -- for useful functions  #include -- for character functions

char Data Type Variables declared char are just integers  Uses standard (ASCII) which translates to characters ‘a’ has value of 97 ‘c’ has value of 100 ‘\n’ has value of 10 Can be used as numeric data type  Typically only handles values -128 to 128 Unfortunately EOF larger than 128

int putchar(int) Functions return value is not really used Prints a single character to the screen  Faster & easier than printf  int argument supports EOF and ‘\n’  Also enables passing a literal value putchar(‘\n’); putchar(97); is equivalent to putchar(‘a’); char val = 97; putchar(97 + 3);

int getchar() Function reads next character from input  Returns as int to support EOF  Normally illegal, but can assign result to char Better than scanf for reading character  Since spaces are characters, includes them  Slow to read actual data however

Converting Letters char toupper(char) – returns uppercase or (if not letter) original character toupper(‘a’)  ‘A’ toupper(‘A’)  ‘A’ toupper(‘7’)  ‘7’ char tolower(char) – returns lowercase or (if not letter) original character tolower(‘a’)  ‘a’ tolower(‘A’)  ‘a’ tolower(‘7’)  ‘7’

Converting Letters toupper & tolower do not change value stored in arguments char b, c, d, e, f, g; b = ‘a’; c = ‘D’; d = toupper(b); e = tolower(c); f = toupper(tolower(d)); g = tolower(c + 1);

Boolean Logic Named after 19 th century mathematician who created system  Forms basis of all computer work World consists of two values: true & false  C uses integers to represent these values  0 equals false in C  Any other value equals true

Boolean Character Functions int isdigit(char)Returns true if a decimal digit; otherwise, returns zero (false) int islower(char)Returns true if a lowercase letter; otherwise, returns zero (false) int isupper(char)Returns true if an uppercase letter; otherwise, returns zero (false) int isalpha(char)Returns true if a letter; otherwise, returns zero (false) int isalnum(char)Returns true if a letter or digit; otherwise, returns zero (false) Many more listed in book

Boolean Results on Gort char ch = ‘a’; char example = ‘D’; printf(“%d %d\n”, isalpha(ch), ispunct(example)); ch = example - 2; example = 48; printf(“%d %d\n”, isalpha(ch), isdigit(example)); ch = tolower(ch + 1); example = ‘\n’; printf(“%d %d\n”, isupper(ch), isspace(example)); Output

Your Turn Get into groups and complete daily activity

For Next Lecture Read Sections 3.1 – 3.3 of book  Do not need to understand all the details  But important knowing what is not understood Complete week #3 weekly assignment Complete lab #2 First programming assignment next week!