Half adder and 1 bit full bit adder

Half Adder

A Half Adder can be see in Fig.1 and Fig.2 below;

Fig.1

Fig.2

This is when we are adding only a single bit, for example, see Fig.3;

Fig.3

Full Adder

A Full Adder can be seen in Fig.4, Fig.5 & Fig.6 below;

Fig.4

Fig.5

Fig.6

If we were to add 1110 and 0111 then referring to Fig.6 above, A0 would be the right most bit of the first number (0) and B0 would be thee right most bit of the second number (1) and so on, moving from right to left, so;

0100 = A3=1, A2=1, A1=1 and A0=0

0111 = B3=0, B2=1, B1=1 and B0=1

S is the result of the individual calculation, so;

S0 = 1

S1 = 0

S2 = 1

S3 = 0

The C is the carry bit naturally, so C2, C3 and C4 = 1

the calculation can be seen below in Fig.7

Fig.7

Figures, reproduced from printed material for personal use.