Add audio

C/audio/README.md

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+# Audio
+
+Compile the program with
+
+
+```bash
+gcc -lm waves.c
+```
+
+Execute and hear the output with
+
+```bash
+./a.out | aplay
+```

C/audio/waves.c

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+///////////////////////////////////////////////////////////////////////////////////////////////////
+// Tyler Perkins
+// 12-30-20
+// Testing command line audio
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <math.h>
+
+int main(int argc, char** argv){
+    if(argc != 1){
+        printf("Usage: %s\n", argv[0]);
+        return -1;
+    }
+
+    //sawtooth wave
+    for(int t=0, osc=0; t<8000; t++, osc += 14){
+        putchar(osc);
+    }
+
+    //square wave
+    for(int t=0, osc=0; t<8000; t++, osc += 14){
+        putchar(osc & 0x80);
+    }
+
+    //sine wave
+    for(int t=0, osc=0; t<8000; t++, osc += 14){
+        putchar(127 * sin(osc/255.0*2*3.1415) + 128);
+    }
+
+    
+    /* kinda bass guitar?
+     *
+     * The idea here is an array full of random data, with 
+     * an array size equal to the period of the wave
+     * (for 440 its ~18) then loop the array. 
+     * Then we average out the current value and next one
+     * Till we get a faded noise to silence
+     *
+     * Pretty cool ngl
+     */
+
+    unsigned char a[18];
+
+    //init the array with random data
+    FILE *fp;
+    fp = fopen("/dev/random", "r");
+    if(fp == NULL){
+        printf("Couldnt open random stream!\n");
+        return -1;
+    }
+    if(fgets(a,sizeof(a),fp)==NULL){
+        printf("Failed to read the random stream!\n");
+        return -1;
+    }
+    fclose(fp);
+
+    //play the bass guitar
+    for(int t=0;t<8000;t++){
+        int i = t % sizeof(a);
+        int j = (t+1) % sizeof(a);
+        putchar(a[i] = (a[i] + a[j])/2);
+    }
+
+    return 0;
+}