You need to be much more specific. The US has printed $100 bills since the 1860s so saying an "old bill" covers A LOT of territory.
Anything dated 1981 or later isn't likely to be worth a premium unless it's uncirculated. If the bill has an earlier date, please check whether there is a small letter next to the date, and what color printing is used for the serial numbers and seal (you DON'T have to copy the serial number, though!) Then post a new question with that specific information.
The value of an old $100 bill depends on its condition, rarity, and year of issue. Generally speaking, a well-circulated old $100 bill may be worth slightly above face value to collectors, while a rare or uncirculated bill could be worth more to a collector or currency enthusiast. It's best to consult with a currency expert or appraiser to determine the exact value of your specific bill.
One is still worth exactly $100, because it's not rare or old enough to be worth more.
$100 bills don't get as much use as smaller denominations so they don't wear out as fast. That means $100 bills as old as 1981 really don't have any added value if they turn up in circulation. However, a nice crisp uncirculated $100 with that date might be worth an additional $10 to $15 at retail.
At a bank, it's still worth face value. To a collector, it could be worth closer to $110. It's not old or rare enough to be worth much more.
it is worth `bout $50-$100
WWII-era military currency may be old, but it isn't worth very much. Every GI in the Pacific came home with a pocket full of bills. Being that it's a larger denomination, it might be worth upwards of a dollar.
Today, nothing. Italy adopted the euro in 2002 and all lira currency was taken out of circulation that year. If you have old lira coins or bills you might be able to find a bank in a major city where you could exchange them but it would hardly be worth the effort. At the exchange rate in effect at the time, 1000 lira were only worth about 75¢
The value depends on the series (date) and condition. If it's series 1976 or later, it's worth face value.
$100
In general coins have higher values.
50-100 USD. 50-100 years old
It all depends on which company made it and what condition it is in.
1000 dollars