|CSC 161||Grinnell College||Fall, 2013|
|Imperative Problem Solving and Data Structures|
C provides two equivalent approaches for reading individual characters.
char ch; ch = getchar();
char ch; scanf ("%c", &ch);
When reading character data with either getchar or %c with scanf, the first character is read and recorded; that is, the process of reading a character does NOT skip over white space.
Some of you may have noticed that Kernighan & Ritchie's book, The C
Programming Language, declares int variables and sets them to char
values, while the above examples declare char variables set
char values. The local system automatically converts
int values that
char values when set to
char variable, so on the local system, these declarations
are valid. Just be aware that some systems may not support this automatic
C also provides at least three approaches for reading strings of characters. Each function has its own special characteristics.
char str; /* allow room for 10 characters, including the null */ scanf ("%s", str); /* since str is an array, the variable represents a base address and no ampersand & is added */
char str; gets (str);
char str; /* stdin is the C variable for "standard input" */ fgets (str, 10, stdin); /* up to 9 characters are read from the terminal, leaving room for a null character at the end */
As with reading character data , stored input starts immediately with the first character read; the process of reading a string does NOT skip over white space.
Warning: Both scanf and gets read characters (until white space or the end of a line), without regard for the size of the string array. If more characters are read than fit in the array, the characters may overflow to fill data stored in other variables. Thus, only fgets can be considered "safe".
Development of laboratory exercises is an interactive process. Prof. Walker welcomes your feedback! Feel free to talk to him during class or stop by his office.