- CBAUD
- CGA
- CGAIO
- CGA_GET
- CHARS
- CHAR_BIT
- CHAR_MAX
- CHAR_MIN
- CHECK_LAST_NR
- CHILD_MAX
- CIBAUD
- CLEAR_INTR
- CLEAR_TIMER
- CLOCAL
- CLOCKS_PER_SEC
- CMOS_READ
- CODE_SPACE
- CONST1
- CONSTL2E
- CONSTL2T
- CONSTLG2
- CONSTLN2
- CONSTPI
- CONSTZ
- CONS_CURRENT
- CONS_GET
- CON_COLS
- CON_ROWS
- COPYBLK
- CR0
- CR1
- CR2
- CR3
- CRDLY
- CREAD
- CRTSCTS
- CS
- CS5
- CS6
- CS7
- CS8
- CSIZE
- CSTOPB
- CT_TO_SECS
- CT_TO_USECS
- CURRENT
- CURRENT_DEV
- CURRENT_TIME
- C_HUP
- C_SPEED