gchq/CyberChef · error · OperationError

Μ37 start must be between 1 and 37

Error message

Μ37 start must be between 1 and 37

What it means

Thrown when the Μ37 (M37) motor wheel start position args[51] is outside 1–37. The Μ37 wheel has 37 cam positions, so the start must be 1–37 inclusive.

Source

Thrown at src/core/operations/Colossus.mjs:438

        };

        const settotal = parseInt(args[42], 10);
        if (settotal < 0 || settotal > 9999)
            throw new OperationError("Set Total must be between 0000 and 9999");

        // null|fast|slow for each of S1-5,M1-2,X1-5
        const control = {
            fast: args[43],
            slow: args[44]
        };

        // Start positions
        if (args[52]<1 || args[52]>43) throw new OperationError("Ψ1 start must be between 1 and 43");
        if (args[53]<1 || args[53]>47) throw new OperationError("Ψ2 start must be between 1 and 47");
        if (args[54]<1 || args[54]>51) throw new OperationError("Ψ3 start must be between 1 and 51");
        if (args[55]<1 || args[55]>53) throw new OperationError("Ψ4 start must be between 1 and 53");
        if (args[56]<1 || args[57]>59) throw new OperationError("Ψ5 start must be between 1 and 59");
        if (args[51]<1 || args[51]>37) throw new OperationError("Μ37 start must be between 1 and 37");
        if (args[50]<1 || args[50]>61) throw new OperationError("Μ61 start must be between 1 and 61");
        if (args[45]<1 || args[45]>41) throw new OperationError("Χ1 start must be between 1 and 41");
        if (args[46]<1 || args[46]>31) throw new OperationError("Χ2 start must be between 1 and 31");
        if (args[47]<1 || args[47]>29) throw new OperationError("Χ3 start must be between 1 and 29");
        if (args[48]<1 || args[48]>26) throw new OperationError("Χ4 start must be between 1 and 26");
        if (args[49]<1 || args[49]>23) throw new OperationError("Χ5 start must be between 1 and 23");

        const starts = {
            X1: args[45], X2: args[46], X3: args[47], X4: args[48], X5: args[49],
            M61: args[50], M37: args[51],
            S1: args[52], S2: args[53], S3: args[54], S4: args[55], S5: args[56]
        };

        const colossus = new ColossusComputer(input, pattern, qbusin, qbusswitches, control, starts, settotal, limit);
        const result = colossus.run();

        return result;
    }

View on GitHub (pinned to 4290ea7539)

Solutions

1. Set args[51] (Μ37 start) to an integer 1–37.
2. Mind arg index: M37 = args[51], M61 = args[50] (reverse of numeric order).
3. Use 1-based indexing.

Example fix

// before
// args[51] = 38
// after
// args[51] = 37

const v = Number(args[51]);
if (!Number.isFinite(v) || v < 1 || v > 37) { /* fix Μ37 start before run */ }

function inRange(v, lo, hi) { const n = Number(v); return Number.isFinite(n) && n >= lo && n <= hi; }

null

When it happens

Trigger: Colossus.run checks args[51]<1 || args[51]>37 and throws otherwise. Note arg indexing is non-sequential (M37 is args[51], M61 is args[50]).

Common situations: User confuses the two motor wheels (M37 vs M61) and their ranges, uses 0-based indexing, or maps starts positionally without checking which arg index each wheel occupies.

Related errors

• Ψ1 start must be between 1 and 43
• Ψ2 start must be between 1 and 47
• Ψ3 start must be between 1 and 51
• Ψ4 start must be between 1 and 53
• Ψ5 start must be between 1 and 59

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/a44b385b13b34fdb. Report an issue: GitHub.