basic C question

Pardon my ignorance. I just can't seems to be able to figure out why
this will not compile:

#include <string.h>
#include <unistd.h>

char hostName[256];
int hostNameLen;

hostNameLen = sizeof(hostName);

gethostname(hostName, hostNameLen);

exit(0);




Below is portion of the compiler error:
4 |

5 | char hostName[256];

6 | int hostNameLen;

7 |

8 | hostNameLen = sizeof(hostName);

===========>
.a......................................................................
..........
*=ERROR===========> a - CZM0273 Missing type in declaration of
hostNameLen.
9 |

10 | gethostname(hostName, hostNameLen);

===========>
.a......................................................................
..........
*=ERROR===========> a - CZM0273 Missing type in declaration of
gethostname.
*=SEVERE==========> a - CZM0282 The type of the parameters must be
specified in a prototype.
11 |

12 | exit(0);

===========>
.b....a.................................................................
..........
*=SEVERE==========> a - CZM0275 Unexpected text integer constant
encountered.
*=ERROR===========> b - CZM0273 Missing type in declaration of exit.

* * * * * E N D O F S O U
R C E * * * * *?