Sew creates binary files from text files. For example,

.format binary
; two bytes, each byte most-significant bit first
10101011 11001101
.format binary_little
; two bytes, each byte least-significant bit first
10000100 11000010

will compile to the four byte binary file conventionally written: 0xab 0xcd 0x21 0x43. Hex is also supported. To create the same file:

.format hex
ab cd
.format hex_little
12 34

cc -o sew sew.c

./sew -o test test.sew