Index: Makefile
==================================================================
--- Makefile
+++ Makefile
@@ -1,6 +1,6 @@
-all: aocdbg aoc aocclang aoctcc
+all: aoc aocdbg aoc aocclang aoctcc
 
 clean:
 	rm aocdbg aoc aocclang aoctcc
 
 aocdbg: *.c *.h

Index: aoc.c
==================================================================
--- aoc.c
+++ aoc.c
@@ -1,5 +1,8 @@
+/* *********************************************************************
+Repository: https://chiselapp.com/user/nnz/repository/AdventOfCode/index
+********************************************************************* */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include "aocdailies.h" // prototypes for all aocYYYYdd functions!
 #include "aocutils.h"

Index: aoc2024.c
==================================================================
--- aoc2024.c
+++ aoc2024.c
@@ -33,10 +33,73 @@
         sum2000 += secret;
         key = strtok(NULL, "\n");
     }
     printf("The sum of all 2000th secrets is {%llu}.\n", sum2000);
 }
+
+/* === aoc202417 =======================================================
+===================================================================== */
+
+static unsigned combo(unsigned operand, unsigned long long r[3]) {
+    switch (operand) {
+        default: fprintf(stderr, "Nope!\n"); exit(EXIT_FAILURE);
+        case 0: return 0;
+        case 1: return 1;
+        case 2: return 2;
+        case 3: return 3;
+        case 4: return (unsigned)(r[0] & 0xFFFFFFFF);
+        case 5: return (unsigned)(r[1] & 0xFFFFFFFF);
+        case 6: return (unsigned)(r[2] & 0xFFFFFFFF);
+    }
+}
+
+static unsigned instruction(unsigned ip, unsigned opcode, unsigned operand,
+                            unsigned long long r[3],
+                            char *out, size_t *outlen) {
+    unsigned nextip = ip + 2;
+    switch (opcode) {
+        default: case 3: if (r[0]) { nextip = operand; } break;
+        case 0: r[0] = r[0] / (1 << combo(operand, r)); break;
+        case 1: r[1] = r[1] ^ operand; break;
+        case 2: r[1] = combo(operand, r) % 8; break;
+        case 4: r[1] = r[1] ^ r[2]; break;
+        case 5: if (*outlen) { out[*outlen] = ','; *outlen += 1; }
+                out[*outlen] = combo(operand, r) % 8 + '0';
+                *outlen += 1;
+                break;
+        case 6: r[1] = r[0] / (1 << combo(operand, r)); break;
+        case 7: r[2] = r[0] / (1 << combo(operand, r)); break;
+    }
+    return nextip;
+}
+
+void aoc202417(char *data, size_t len) {
+    (void)len; //unused argument
+    unsigned long long reg[4]; // A, B, and C ... and copy of A for Part Two
+    char *dta = strstr(data, " A: "), *err;
+    reg[0] = strtoull(dta + 4, &err, 10);
+    dta = strstr(err, " B: ");
+    reg[1] = strtoull(dta + 4, &err, 10);
+    dta = strstr(err, " C: ");
+    reg[2] = strtoull(dta + 4, &err, 10);
+    dta = strstr(err, "Program: ") + 9;
+    unsigned p[100] = {0}, np = 0;
+    while (dta && *dta) {
+        unsigned v = strtoul(dta, &err, 10);
+        p[np++] = v;
+        if (*err == 0) dta = NULL;
+        else dta = err + 1; // skip comma
+    }
+    char output[1000];
+    size_t outlen = 0;
+    unsigned ip = 0;
+    while (ip + 1 < np) {
+        ip = instruction(ip, p[ip], p[ip+1], reg, output, &outlen);
+    }
+    output[outlen] = 0;
+    printf("Program's output is {%s}\n", output);
+}
 
 /* === aoc202409 =======================================================
    WOW! input consists of a 20,000 long string of numbers!
    Make an array of blocks, each with either -1 or the fileid
    For Part Two: make an array of blocks with the encoded value of

Index: aocdailies.c
==================================================================
--- aocdailies.c
+++ aocdailies.c
@@ -6,10 +6,11 @@
     switch (y * 100 + d) {
         default: p = NULL; break;
 
         //   YYYYdd ==>  aocYYYYdd
         case 202422: p = aoc202422; break;
+        case 202417: p = aoc202417; break;
         case 202409: p = aoc202409; break;
         case 202408: p = aoc202408; break;
         case 202407: p = aoc202407; break;
         case 202406: p = aoc202406; break;
         case 202405: p = aoc202405; break;

Index: aocdailies.h
==================================================================
--- aocdailies.h
+++ aocdailies.h
@@ -5,10 +5,11 @@
 
 typedef void aocfunc(char *, size_t);
 aocfunc *aocselect(unsigned, unsigned);
 
 aocfunc aoc202422;
+aocfunc aoc202417;
 aocfunc aoc202409;
 aocfunc aoc202408;
 aocfunc aoc202407;
 aocfunc aoc202406;
 aocfunc aoc202405;