KwickClips Computer Systems · 43 sec · free
What are sum and carry for three 1s?
Short answer. Both 1.
When is the carry out 1?
When two or more inputs are 1.
Count the 1s
| Ones in | Sum | Cout |
|---|---|---|
| 0 | 0 | 0 |
| 1 | 1 | 0 |
| 2 | 0 | 1 |
| 3 | 1 | 1 |
Remember
| Sum 1: odd number of 1s |
| Cout 1: two or more 1s |
Three input bits. How do you find sum and carry fast? Just count the ones. None gives zero, zero. One gives sum one. Two gives carry one. Three gives both one. Two rules. Odd ones make sum one. Two or more make carry one.
This clip is from the full lesson: Adders and Combinational Circuits: Half Adder and Full Adder — 8 minutes, with the tables, the quick answers and the whole lesson in text.
Useful for: ISC Class 11 Computer Science (868), ISC Class 12 Computer Science (868), ISC Class 12 Computer Science (868), Programming All levels C
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