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MODULE V - FUNDAMENTALS OF ELECTRONICS DIGITAL BASICS  (Continuation) Binary Numbers and Hex-Decimal in Digital Basics If you have a single switch or input you can have two possible input states, it is either on or off. With two switches or inputs you have four possible input states as shown above. If you go to three inputs you have eight possible states and four inputs give you sixteen states. Again digital basics. By adding another input you double the previous number of states. Doubling the inputs gives you the square of the states. We say four inputs gives sixteen states so doubling that gives us eight inputs so the number of states should be 16 X 16 or 256.

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Consider this. If I offered you a job and I made you two alternative offers for monthly payment - Offer No. 1 is to pay you a most generous $10,000.00 for the month. Offer No. 2 is to pay you one cent for the first day you work for me, two cents the next day and doubling each day thereafter for the whole 30 day month. Which offer would you accept? Answer at the very bottom of this page. Binary Coded Decimal To the right we have provided a table of BCD data which is all based upon the old "1's" and "0's". If at first it looks a bit intimidating don't worry you will very quickly get the hang of it. Notice first of all we have in the extreme right hand column the numbers 0 - 9 and the letters A to F. The first four columns are headed 8 - 4 -2 - 1 We explained earlier by adding switches you double the previous capacity for numbering in binary. Notice the pattern of our 0's and 1's. Under the column 1 we get a succession of 0, 1, 0, 1.....  Under the column 2 we get a succession of 0, 0, 1, 1..... etc. In fact under every column heading you have exactly an equal number of zeros first  followed by the same number of ones. Look at column 8 for example. Eight zeros followed by eight ones. Now look at the far right column and look up number seven, follow that row reading across right to left and you will see the sequence 0 - 1 - 1 - 1. Okay if a one means a turned on switch with the value of that column what does 4 + 2 + 1 =? Binary Coded Decimal - BCD 8 4 2 1   0 0 0 0 0 0 0 0 1 1 0 0 1 0 2 0 0 1 1 3 0 1 0 0 4 0 1 0 1 5 0 1 1 0 6 0 1 1 1 7 1 0 0 0 8 1 0 0 1 9 1 0 1 0 A 1 0 1 1 B 1 1 0 0 C 1 1 0 1 D 1 1 1 0 E 1 1 1 1 F Of course the answer was seven. Try it with any number you like. Alright what's this A to F stuff? Look at a digit on a digital clock or watch for example. For those numbers to be represented in digital format requires four switches but now we will start using the correct terms. The word is "bits", heard that before? Now we're right into digital basics. Four bits are called "a nibble" and guess what?, eight bits are called "a byte". Bet you've heard that one for sure unless you live under a rock. You should know by now that four switches (OK bits right!) can represent sixteen states and with a digital clock you only go 0 to 9 and don't need anything else so that was called BCD or Binary Coded Decimal. The last word is because we humans count in decimal format or decades. Digital devices including computers DON'T, they can't. All they see are ones and zeros, nothing else. Digital Basics - Final Page >>>

Electron Theory and Atoms Resistance Resistors Ohms Law Current and Voltage Voltage Dividers Capacitance Inductance Reactance Resonance and Impedance Diodes Transistors "Q" Radio Terminology A-L Radio Terminology M-Z Atttenuators Chokes Decibel & Toroids Digital Basics Power Supplies Conclusion  Subscribe For A Free Ham Radio E-Tutorials  Back To Top

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