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{{implementation|bc}}

This is the `/usr/bin/bc` on [[OpenBSD]] systems. It has some, but not all, of the features as [[GNU bc]].

- [http://www.openbsd.org/cgi-bin/man.cgi?query=bc&apropos=0&sektion=1&manpath=OpenBSD+Current&arch=i386&format=html OpenBSD bc(1) manual page]
- [http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/bc/ src/usr.bin/bc/]

These extensions are in OpenBSD bc but not in [[POSIX]]:

- Two new options,
`bc -c`and`bc -e`. - Long names (more than one letter) for variables and functions.
`# Line comments.`- Relational operators (
`== <= >= !- < >`) in any expression, not only in 'if', 'while' or 'for'. - Boolean operators (
`! && ||`). `else`branch of an 'if' statement.`print`statement, with escapes like '\n'.- Special variable
`last`, also known as`.`(a single dot).

The most unique feature of OpenBSD bc is that it runs on top of [[dc]]. (The original AT&T bc also did this, but GNU bc does not.) OpenBSD bc translates the entire program from bc to dc, then calls [[OpenBSD dc]] `/usr/bin/dc` to run the program. (OpenBSD dc has several extensions to allow this to work.)

The `bc -c` option just skips the second step, so we can see how OpenBSD translates a program from [[bc]] to [[dc]]. Here follows an example with the [[Fibonacci sequence]].

- '''Program using bc'''

```
$ cat prog.bc
# compute fib[0] thru fib[19]
fib[0] = 0
fib[1] = 1
for (i = 2; i < 20; i++) {
fib[i] = fib[i - 1] + fib[i - 2]
}
# print fib[a] thru fib[b]
define fib(a, b) {
auto i
print "fib ", a, "..", b, " = "
for (i = a; i <= b; i++) {
print fib[i]
if (i < b) print ", " else print "\n"
}
}
# assignments to prevent printing of trash
trash = fib(0, 4)
trash = fib(15, 19)
quit
```

- '''Translation to dc'''

```
$ bc -c prog.bc | vis
0 0:\M^?\^A\^A
1 1:\M^?\^A\^A
[li 1-;\M^?\^A\^Ali 2-;\M^?\^A\^A+li:\M^?\^A\^Alid1+sis.li 20>0]s0
2dsis.li 20>0
[[, ]n]s1
[[
]n]s2
[li;\M^?\^A\^Ads.nlilb>1e2 lid1+sis.lilb!<0]s0
[0SiSbSa[fib ]nlads.n[..]nlbds.n[ = ]nladsis.lilb!<0 Las.Lbs.Lis.0 1Q]s\M^?\^A\^B
0 4l\M^?\^A\^Bxs\M^?\^A\^C
15 19l\M^?\^A\^Bxs\M^?\^A\^C
q
```

- '''Output'''
$ bc -c prog.bc | dc -x # or simply $ bc prog.bc fib 0..4 = 0, 1, 1, 2, 3 fib 15..19 = 610, 987, 1597, 2584, 4181

```
```