SuperCalc worksheet (.cal)
.cal file signature | application/octet-stream
The SuperCalc worksheet (CAL) is a spreadsheet file format used by the SuperCalc application, originally developed by Sorcim and later maintained by Computer Associates. It was used to store worksheets containing cell data, formulas, and basic spreadsheet layout for business, accounting, and personal calculations. The format is now largely legacy and may require older software or converters to open, but it does not present notable security risks beyond the usual caution for untrusted documents.
Magic Bytes
Offset 0
53 75 70 65 72 43 61 6C 63
Sources: Gary Kessler
All Known Signatures
3 signature variants are documented for .cal files across multiple sources.
| Hex Signature | Offset | Sources |
|---|---|---|
| 53 75 70 65 72 43 61 6C 63 | 0 | Gary Kessler |
| 73 72 63 64 6F 63 69 64 3A | 0 | Gary Kessler |
| B5 A2 B0 B3 B3 B0 A5 B5 | 0 | Gary Kessler |
Extension
.cal
MIME Type
application/octet-stream
Byte Offset
0
Risk Level
Safe
Validation Code
How to validate .cal files in Python
def is_cal(file_path: str) -> bool:
"""Check if file is a valid CAL by magic bytes."""
signature = bytes([0x53, 0x75, 0x70, 0x65, 0x72, 0x43, 0x61, 0x6C, 0x63])
with open(file_path, "rb") as f:
return f.read(9) == signatureHow to validate .cal files in Node.js
function isCAL(buffer: Buffer): boolean {
const signature = Buffer.from([0x53, 0x75, 0x70, 0x65, 0x72, 0x43, 0x61, 0x6C, 0x63]);
return buffer.subarray(0, 9).equals(signature);
}How to validate .cal files in Go
func IsCAL(data []byte) bool {
signature := []byte{0x53, 0x75, 0x70, 0x65, 0x72, 0x43, 0x61, 0x6C, 0x63}
if len(data) < 9 {
return false
}
return bytes.Equal(data[:9], signature)
}API Endpoint
/api/v1/cal
curl https://filesignature.org/api/v1/cal
See the full API documentation for all endpoints and parameters.
Frequently Asked Questions
What is a .cal file?
A .cal file is a SuperCalc worksheet file. The SuperCalc worksheet (CAL) is a spreadsheet file format used by the SuperCalc application, originally developed by Sorcim and later maintained by Computer Associates. It was used to store worksheets containing cell data, formulas, and basic spreadsheet layout for business, accounting, and personal calculations. The format is now largely legacy and may require older software or converters to open, but it does not present notable security risks beyond the usual caution for untrusted documents.
What are the magic bytes for .cal files?
The magic bytes for SuperCalc worksheet files are 53 75 70 65 72 43 61 6C 63 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.
How do I validate a .cal file?
To validate a .cal file, read the first bytes of the file and compare them against the known magic bytes (53 75 70 65 72 43 61 6C 63) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.
What is the MIME type for .cal files?
There is no officially registered MIME type for .cal files. Systems typically use application/octet-stream as a generic fallback when handling this format.
Is it safe to open .cal files?
SuperCalc worksheet (.cal) files are generally safe to open. They are classified as low risk because they primarily contain data rather than executable code. However, always ensure files come from a trusted source.