How to select fuses?

[young]

for a 12f675 device there is
LP Low power osc < 200 khz
XT Crystal osc <= 4mhz
INTRC Internal RC Osc
HS High speed Osc (> 4mhz)
NOWDT No Watch Dog Timer
WDT Watch Dog Timer
CPD Data EEPROM Code Protected
NOCPD No EE protection
PROTECT Code protected from reads
NOPROTECT Code not protected from reading
NOMCLR Master Clear pin used for I/O
MCLR Master Clear pin enabled
PUT Power Up Timer
NOPUT No Power Up Timer
RC Resistor/Capacitor Osc with CLKOUT
EC External clock with CLKOUT
RC_IO Resistor/Capacitor Osc
INTRC_IO Internal RC Osc, no CLKOUT
BROWNOUT Reset when brownout detected
NOBROWNOUT No brownout reset

in the program, according to what to select them, for example, how do you know you to select INTRC, HS, XT? why select NO watchdog timer instead of watch dog timer, etc.?

[SherpaDoug]

If you are asking HOW to specify which fuses, there are many examples on this board.
If you want to know WHY one would select certain fuses you should read the chip data sheet. For example XT and HS are determined by the clock source, whether it is an external logic clock or a crystal and if so what frequency crystal. Internally it controls the gain of the oscillator circuit.
One might choose NOWDT if the watchdog becomes annoying during debugging or if resetting the processor is not helpful. For example I believe some PICs are used for internal timing of some of the larger fireworks. It that case you want it to run or die trying. Resetting and trying again later is not an option because by then the shell will have fallen on somebody's head.
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