![]() Repeat until a letter separator is reached, at that point the index inside the lookup string will point to the ASCII corresponding to the decoded morse. At every received element (dot or dash) halve the initial dash jump and then increase by 1 the index inside the lookup string if a dot was received and by dash jump size if a dash was received. Have an index inside the lookup string inizialied to zero. The algorithm can be decribed as follows. Below is a concise description of how the algorithm works but make sure you take the time to read project description in its entirety. This provides enough room for A-Z and 0-9 without chance of collision but could be expanded to allow for more characters. What makes this really stand out is a brilliant algorithm that allows conversion from Morse to ASCII using a lookup table of only 64 bytes. We think project is well worth featuring simply based on his explanation of the Digital Signal Processing used on the signal coming in from the microphone. This one takes a tack and builds an automatic decoder. Often the Morse Code centered projects that we feature are to help you practice transmitting messages. This entry was posted in Lesson by dgookin. In next week's Lesson I show some improvements to the code, which properly presents the output. It's not an attempt at encryption or obfuscation, so making it pretty is a good thing. Second, the code could be formatted in a manner other than a long string of hex bytes. First, the output isn't identifiable as encoded data, so a heading would help not only anyone reading the data but eventually assist the decoding program to recognize properly-encoded data. Here’s a sample run at the command prompt: Hello there, Dan!Īssuming the program is named 1024 and you have a file named gettysburg.txt in the current directory, you can use the filter with input redirection to encode the file’s text. Press Ctrl+C to end input or, to generate the EOF character, type Ctrl+Z in Windows or Ctrl+D in Unix. If you run the code by itself, type some text and press the Enter key to see it processed. You can run it by itself, which is weird, or redirect input from another source. Yes, this program is a filter, which reads standard input and generates standard output. Otherwise, the value of ch is XOR’d with 0xAA in the printf() statement at Line 12, and output as a 2-digit hexadecimal byte. If the end of file is captured at Line 10, the loop halts. Standard input is read at Line 9 and stored in variable ch. The while loop at Lines 7 through 13 is endless. The following code reads text from standard input and outputs a string of hexadecimal bytes encoded with XOR 0xAA. If you XOR 0xAA any byte and then XOR 0xAA the result, you get back the original value. Send those values into another program to decode and retrieve the original text.Īnother example, one I touch upon in my books, is the exclusive OR operation using byte 0xAA, binary 10101010. In all cases, the original data is recovered, which is the point of encoding and decoding.Ī simple example of encoding would be to input a string as text and output that string as its ASCII code values, using either decimal or hex values. ![]() As with encoding, you can compress and decompress data, encrypt it or decrypt it, or a mixture of each. While these could be attributes of encoding, they’re not required features. For example, Morse Code translates letters and numbers into dots and dashes.Īt the other end, decoding translates the code created back into its original form, such as taking the dots and dashes and converting them back into readable text.ĭon’t confuse encoding with compression or encryption. This process makes you think about data and how it’s represented, and also how to work on both ends of an input/output puzzle.Įncoding is the process of translating information into another format. ![]() A good way to exercise your C programming muscles is to work on a encoding/decoding project.
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