The Apollo missions had technology no more complicated than a pocket calculator. 

From link [**here**][1], there's an information about Apollo Guidance Computer (AGC)

> The on-board Apollo Guidance Computer (AGC) was about 1 cubic foot with 2K of 16-bit RAM and 36K of hard-wired core-rope memory with copper wires threaded or not threaded through tiny magnetic cores. The 16-bit words were generally 14 bits of data (or two op-codes), 1 sign bit, and 1 parity bit. The cycle time was 11.7 micro-seconds. Programming was done in assembly language and in an interpretive language, in reverse Polish.

So, I've stumbled upon some source code when I researched what was up there, and I've noticed great comments (eg. TEMPORARY, I HOPE HOPE HOPE)

 VRTSTART	TS	WCHVERT
 # Page 801
 		CAF	TWO		# WCHPHASE = 2 ---> VERTICAL: P65,P66,P67
 		TS	WCHPHOLD
 		TS	WCHPHASE
 		TC	BANKCALL	# TEMPORARY, I HOPE HOPE HOPE
 		CADR	STOPRATE	# TEMPORARY, I HOPE HOPE HOPE
 		TC	DOWNFLAG	# PERMIT X-AXIS OVERRIDE
 		ADRES	XOVINFLG
 		TC	DOWNFLAG
 		ADRES	REDFLAG
 		TCF	VERTGUID

My question here is this:

 - How were the teams writing this much code able to make it functional given the tools at the time?

Because if you compile so much code that was used on Apollo 11... it'd take days, even weeks. I seriously doubt that programmers back then left everything to happen by chance. 


 [1]: http://www.hq.nasa.gov/alsj/a11/a11.1201-fm.html