HANDLING STANDARD INPUT AND OUTPUT

Objectives:

• Learn about standard input and output functions in C, including:

  • printf()

  • getc()

  • putc()

  • getchar()

  • putchar()

UNDERSTANDING STANDARD I/O

• In C, files are treated as a series of bytes or a stream.

• All file streams are treated equally, whether they come from a disk, terminal, or other sources.

• Three pre-opened file streams are available:

  • stdin for standard input

  • stdout for standard output

  • stderr for standard error

Using the getc() Function

• getc() reads the next character from a file stream and returns it as an integer.

• Syntax: int getc(FILE *stream);

• Example:

  int ch;
  ch = getc(stdin);

Using the getchar() Function

• getchar() is equivalent to getc(stdin).

• Syntax: int getchar(void);

• Example:

  int ch;
  ch = getchar();

Using the putc() Function

• putc() writes a character to a file stream, such as stdout.

• Syntax: int putc(int c, FILE *stream);

Example: Outputting a character with putc():

int ch;
ch = 65; // Numeric value of 'A'
putc(ch, stdout);

Using the putchar() Function

• putchar() is similar to putc() but uses stdout as the default file stream.

• Syntax: int putchar(int c);

• Example: Outputting characters with putchar():

  putchar(65);
  putchar(10); // Newline

The printf() Function

• printf() is used for formatted output in C.

• Syntax: int printf(const char *format, ...);

• Format specifiers include %c, %d, %i, %f, %e, %E, %g, %G, %o, %s, %u, %x, %X, %p, %n, %%, and more.

• You can use format specifiers to control the output format.

  Example: Converting to hex numbers:

  printf("%X %x %d\n", 10, 10, 10);

Specifying the Minimum Field Width

• You can specify the minimum field width in printf() using %Xd where X is the width.

• Example:

  printf("%5d\n", 10);
  printf("%05d\n", 10); // Padded with zeros

LEFT- OR RIGHT-JUSTIFIED OUTPUT

• You can align output using format specifiers:

  • %Xd for right-justified

  • %-Xd for left-justified

• Example:

  printf("%8d %-8d\n", num1, num1);

USING PRECISION SPECIFIERS

• Precision specifiers can be used to control the format of output.

• Example:

  printf("%2.8d\n", 123);
  printf("%-10.2f\n", 123.45);

SUMMARY

• C treats files as streams of bytes.

• stdin, stdout, and stderr are pre-opened file streams.

• Functions like getc(), getchar(), putc(), putchar(), and printf() are used for I/O.

• Format specifiers control output format, including width and alignment.

• %x or %X can be used to convert decimal numbers to hex numbers.