# `⎕` — Output and input

Keys: `Alt-q`

`⎕←Y` explicitly prints `Y` and retains its value.

``` bpl
≥⎕←2              ⍝ 3
```

The example prints `2` before returning `3`. Explicit output is separate
from implicit result display and is captured by the evaluation API.

## Input

Reading `⎕` gives the next line of standard input as a string, without
its line ending. At the end of the input it gives `⍬`, not the `""` of
an empty line. `⍎⎕` evaluates the line, as Dyalog’s `⎕` does.
`•nget "-"` gives the rest of standard input as one string.

``` bash
printf '3\n4\n' | bpl -e '+/⍎¨[⎕ ⎕]'       # 7
```

`"-" •nput text` writes `text` to standard output with no line ending
added. When `⎕` is read, the text written since the last line ending is
its prompt. A terminal shows the prompt and reads the answer on the same
line, and a notebook shows the prompt beside its text box.

``` bash
printf 'bob\n' | bpl -e '"-" •nput "Name? " ⋄ "Hi ",⎕'   # Name? Hi bob
```

`bpl -e`, script files and the interactive REPL read standard input. In
a notebook, `⎕` asks for a line in a text box, but `•nget "-"` is an
`IO` error. The Python API reads each line with Python’s `input()`, and
`•nget "-"` reads `sys.stdin`. `bpl -` and piped REPL input read the
program itself from standard input. In those two modes and in
`bpl --worker`, reading `⎕` or `•nget "-"` is an `IO` error.

Dyalog’s `⎕A` and `⎕D` are BPL’s [`$a` and
`$d`](../system/constants.qmd). `⎕C` and `⎕UCS` are
[`•c`](../system/c.qmd) and [`•ucs`](../system/ucs.qmd).