Next: Terminal Input, Up: Basic Input and Output

#### 14.1.1 Terminal Output

Since Octave normally prints the value of an expression as soon as it has been evaluated, the simplest of all I/O functions is a simple expression. For example, the following expression will display the value of ``pi`'

         pi
              -| pi = 3.1416

This works well as long as it is acceptable to have the name of the variable (or ``ans`') printed along with the value. To print the value of a variable without printing its name, use the function `disp`.

The `format` command offers some control over the way Octave prints values with `disp` and through the normal echoing mechanism.

— Automatic Variable: ans

> The most recently computed result that was not explicitly assigned to a variable. For example, after the expression

>               3^2 + 4^2

> is evaluated, the value returned by `ans` is 25.

— Built-in Function: disp (x)

> Display the value of x. For example,

>               disp ("The value of pi is:"), disp (pi)

>                    -| the value of pi is:
>                    -| 3.1416

> Note that the output from `disp` always ends with a newline.

> If an output value is requested, `disp` prints nothing and returns the formatted output in a string.

> See also: fdisp.

— Command: format options

> Control the format of the output produced by `disp` and Octave's normal echoing mechanism. Valid options are listed in the following table.

> `short`
>   Octave will try to print numbers with at least 5 significant figures within a field that is a maximum of 10 characters wide (not counting additional spacing that is added between columns of a matrix).

>   If Octave is unable to format a matrix so that columns line up on the decimal point and all the numbers fit within the maximum field width, it switches to an ``e`' format.

> `long`
>   Octave will try to print numbers with at least 15 significant figures within a field that is a maximum of 20 characters wide (not counting additional spacing that is added between columns of a matrix).

>   As will the ``short`' format, Octave will switch to an ``e`' format if it is unable to format a matrix so that columns line up on the decimal point and all the numbers fit within the maximum field width.

> `long e`
> `short e`
>   The same as ``format long`' or ``format short`' but always display output with an ``e`' format. For example, with the ``short e`' format, `pi` is displayed as `3.14e+00`.
> `long E`
> `short E`
>   The same as ``format long e`' or ``format short e`' but always display output with an uppercase ``E`' format. For example, with the ``long E`' format, `pi` is displayed as `3.14159265358979E+00`.
> `long g`
> `short g`
>   Choose between normal ``long`' (or ``short`') and ``long e`' (or ``short e`') formats based on the magnitude of the number. For example, with the ``short g`' format, `pi .^ [2; 4; 8; 16; 32]` is displayed as

>                      ans =

>                            9.8696
>                            97.409
>                            9488.5
>                        9.0032e+07
>                        8.1058e+15

> `long G`
> `short G`
>   The same as ``format long g`' or ``format short g`' but use an uppercase ``E`' format. For example, with the ``short G`' format, `pi .^ [2; 4; 8; 16; 32]` is displayed as

>                      ans =

>                            9.8696
>                            97.409
>                            9488.5
>                        9.0032E+07
>                        8.1058E+15

> `free`
> `none`
>   Print output in free format, without trying to line up columns of matrices on the decimal point. This also causes complex numbers to be formatted like this ``(0.604194, 0.607088)`' instead of like this ``0.60419 + 0.60709i`'.
> `bank`
>   Print in a fixed format with two places to the right of the decimal point.
> `+`
> `+` chars
> `plus`
> `plus` chars
>   Print a ``+`' symbol for nonzero matrix elements and a space for zero matrix elements. This format can be very useful for examining the structure of a large matrix.

>   The optional argument chars specifies a list of 3 characters to use for printing values greater than zero, less than zero and equal to zero. For example, with the ``+ "+-."`' format, `[1, 0, -1; -1, 0, 1]` is displayed as

>                      ans =

>                      +.-
>                      -.+

> `native-hex`
>   Print the hexadecimal representation numbers as they are stored in memory. For example, on a workstation which stores 8 byte real values in IEEE format with the least significant byte first, the value of `pi` when printed in `hex` format is `400921fb54442d18`. This format only works for numeric values.
> `hex`
>   The same as `native-hex`, but always print the most significant byte first.
> `native-bit`
>   Print the bit representation of numbers as stored in memory. For example, the value of `pi` is

>                      01000000000010010010000111111011
>                      01010100010001000010110100011000

>   (shown here in two 32 bit sections for typesetting purposes) when printed in bit format on a workstation which stores 8 byte real values in IEEE format with the least significant byte first. This format only works for numeric types.

> `bit`
>   The same as `native-bit`, but always print the most significant bits first.
> `compact`
>   Remove extra blank space around column number labels.
> `loose`
>   Insert blank lines above and below column number labels (this is the default).
> `rat`
>   Print a rational approximation. That is the values are approximated by one small integer divided by another.

> By default, Octave will try to print numbers with at least 5 significant figures within a field that is a maximum of 10 characters wide.

> If Octave is unable to format a matrix so that columns line up on the decimal point and all the numbers fit within the maximum field width, it switches to an ``e`' format.

> If `format` is invoked without any options, the default format state is restored.

— Built-in Function: val = print_answer_id_name ()
— Built-in Function: old_val = print_answer_id_name (new_val)

> Query or set the internal variable that controls whether variable names are printed along with results produced by evaluating an expression.