Figuring out how a number is represented in hex form
Currently trying to essentially reverse engineer a file format that is produced by a CNC machine when backing up programs on the machine so that i can read the programs on a standard PC. Have opened a few of the backup files created and can clearly see patterns of data such as the program name etc. which can be clearly seen in plaintext form. One thing i am struggling with is how numbers are represented in this.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
More examples:
"-213.6287": "21 67 DF FF"
"-500.3366": "9A A7 B3 FF"
Any help with trying to figure out how these hex values make up those numbers?
Thanks
reverse-engineering binaryfiles
asked Jan 19 at 23:38
jaypjayp
31
add a comment |
Currently trying to essentially reverse engineer a file format that is produced by a CNC machine when backing up programs on the machine so that i can read the programs on a standard PC. Have opened a few of the backup files created and can clearly see patterns of data such as the program name etc. which can be clearly seen in plaintext form. One thing i am struggling with is how numbers are represented in this.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
More examples:
"-213.6287": "21 67 DF FF"
"-500.3366": "9A A7 B3 FF"
Any help with trying to figure out how these hex values make up those numbers?
Thanks
reverse-engineering binaryfiles
asked Jan 19 at 23:38
jaypjayp
31
1
If I was you I'd keep reversing - there is no way that20decimal has any direct correlation with40 0D 03 00hex. So maybe it isn't storing decimal amounts directly, maybe it's a vector or something else instead?
– slugster
Jan 19 at 23:43
add a comment |
Currently trying to essentially reverse engineer a file format that is produced by a CNC machine when backing up programs on the machine so that i can read the programs on a standard PC. Have opened a few of the backup files created and can clearly see patterns of data such as the program name etc. which can be clearly seen in plaintext form. One thing i am struggling with is how numbers are represented in this.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
More examples:
"-213.6287": "21 67 DF FF"
"-500.3366": "9A A7 B3 FF"
Any help with trying to figure out how these hex values make up those numbers?
Thanks
reverse-engineering binaryfiles
asked Jan 19 at 23:38
jaypjayp
31
Currently trying to essentially reverse engineer a file format that is produced by a CNC machine when backing up programs on the machine so that i can read the programs on a standard PC. Have opened a few of the backup files created and can clearly see patterns of data such as the program name etc. which can be clearly seen in plaintext form. One thing i am struggling with is how numbers are represented in this.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
More examples:
"-213.6287": "21 67 DF FF"
"-500.3366": "9A A7 B3 FF"
Any help with trying to figure out how these hex values make up those numbers?
Thanks
reverse-engineering binaryfiles
reverse-engineering binaryfiles
asked Jan 19 at 23:38
jaypjayp
31
asked Jan 19 at 23:38
jaypjayp
31
asked Jan 19 at 23:38
jaypjayp
31
asked Jan 19 at 23:38
jaypjayp
31
asked Jan 19 at 23:38
jaypjayp
31
31
1
If I was you I'd keep reversing - there is no way that20decimal has any direct correlation with40 0D 03 00hex. So maybe it isn't storing decimal amounts directly, maybe it's a vector or something else instead?
– slugster
Jan 19 at 23:43
add a comment |
1
If I was you I'd keep reversing - there is no way that20decimal has any direct correlation with40 0D 03 00hex. So maybe it isn't storing decimal amounts directly, maybe it's a vector or something else instead?
– slugster
Jan 19 at 23:43
1
1
If I was you I'd keep reversing - there is no way that
20 decimal has any direct correlation with 40 0D 03 00 hex. So maybe it isn't storing decimal amounts directly, maybe it's a vector or something else instead?– slugster
Jan 19 at 23:43
If I was you I'd keep reversing - there is no way that
20 decimal has any direct correlation with 40 0D 03 00 hex. So maybe it isn't storing decimal amounts directly, maybe it's a vector or something else instead?– slugster
Jan 19 at 23:43
add a comment |
1 Answer
1
active
oldest
votes
These numbers are stored as little-endian signed integers, as a count of ten-thousandths.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
0x00030d40 = 200000.
"-213.6287": "21 67 DF FF"
0xffdf6721 = -2136287.
"-500.3366": "9A A7 B3 FF"
0xffb3a79a = -5003366.
answered Jan 19 at 23:50
duskwuffduskwuff
147k19177233
Just realised this as i was analysising the hex values. How is the location of the decimal point decided in this though?
– jayp
Jan 20 at 0:00
Based on the examples you've given, the scaling factor (of 10,000) may just be inherent to the format, or the device.
– duskwuff
Jan 20 at 0:06
Yep seems like you're right! just had a scan through the rest of the file and you are right by saying its inherent to the format :) thank you so much for the help!
– jayp
Jan 20 at 0:29
add a comment |
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1 Answer
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1 Answer
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oldest
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These numbers are stored as little-endian signed integers, as a count of ten-thousandths.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
0x00030d40 = 200000.
"-213.6287": "21 67 DF FF"
0xffdf6721 = -2136287.
"-500.3366": "9A A7 B3 FF"
0xffb3a79a = -5003366.
answered Jan 19 at 23:50
duskwuffduskwuff
147k19177233
Just realised this as i was analysising the hex values. How is the location of the decimal point decided in this though?
– jayp
Jan 20 at 0:00
Based on the examples you've given, the scaling factor (of 10,000) may just be inherent to the format, or the device.
– duskwuff
Jan 20 at 0:06
Yep seems like you're right! just had a scan through the rest of the file and you are right by saying its inherent to the format :) thank you so much for the help!
– jayp
Jan 20 at 0:29
add a comment |
These numbers are stored as little-endian signed integers, as a count of ten-thousandths.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
0x00030d40 = 200000.
"-213.6287": "21 67 DF FF"
0xffdf6721 = -2136287.
"-500.3366": "9A A7 B3 FF"
0xffb3a79a = -5003366.
answered Jan 19 at 23:50
duskwuffduskwuff
147k19177233
Just realised this as i was analysising the hex values. How is the location of the decimal point decided in this though?
– jayp
Jan 20 at 0:00
Based on the examples you've given, the scaling factor (of 10,000) may just be inherent to the format, or the device.
– duskwuff
Jan 20 at 0:06
Yep seems like you're right! just had a scan through the rest of the file and you are right by saying its inherent to the format :) thank you so much for the help!
– jayp
Jan 20 at 0:29
add a comment |
These numbers are stored as little-endian signed integers, as a count of ten-thousandths.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
0x00030d40 = 200000.
"-213.6287": "21 67 DF FF"
0xffdf6721 = -2136287.
"-500.3366": "9A A7 B3 FF"
0xffb3a79a = -5003366.
answered Jan 19 at 23:50
duskwuffduskwuff
147k19177233
These numbers are stored as little-endian signed integers, as a count of ten-thousandths.
for Example: the number '20' is represented in this file in hex form as '40 0D 03 00'.
0x00030d40 = 200000.
"-213.6287": "21 67 DF FF"
0xffdf6721 = -2136287.
"-500.3366": "9A A7 B3 FF"
0xffb3a79a = -5003366.
answered Jan 19 at 23:50
duskwuffduskwuff
147k19177233
answered Jan 19 at 23:50
duskwuffduskwuff
147k19177233
answered Jan 19 at 23:50
duskwuffduskwuff
147k19177233
answered Jan 19 at 23:50
duskwuffduskwuff
147k19177233
147k19177233
Just realised this as i was analysising the hex values. How is the location of the decimal point decided in this though?
– jayp
Jan 20 at 0:00
Based on the examples you've given, the scaling factor (of 10,000) may just be inherent to the format, or the device.
– duskwuff
Jan 20 at 0:06
Yep seems like you're right! just had a scan through the rest of the file and you are right by saying its inherent to the format :) thank you so much for the help!
– jayp
Jan 20 at 0:29
add a comment |
Just realised this as i was analysising the hex values. How is the location of the decimal point decided in this though?
– jayp
Jan 20 at 0:00
Based on the examples you've given, the scaling factor (of 10,000) may just be inherent to the format, or the device.
– duskwuff
Jan 20 at 0:06
Yep seems like you're right! just had a scan through the rest of the file and you are right by saying its inherent to the format :) thank you so much for the help!
– jayp
Jan 20 at 0:29
Just realised this as i was analysising the hex values. How is the location of the decimal point decided in this though?
– jayp
Jan 20 at 0:00
Just realised this as i was analysising the hex values. How is the location of the decimal point decided in this though?
– jayp
Jan 20 at 0:00
Based on the examples you've given, the scaling factor (of 10,000) may just be inherent to the format, or the device.
– duskwuff
Jan 20 at 0:06
Based on the examples you've given, the scaling factor (of 10,000) may just be inherent to the format, or the device.
– duskwuff
Jan 20 at 0:06
Yep seems like you're right! just had a scan through the rest of the file and you are right by saying its inherent to the format :) thank you so much for the help!
– jayp
Jan 20 at 0:29
Yep seems like you're right! just had a scan through the rest of the file and you are right by saying its inherent to the format :) thank you so much for the help!
– jayp
Jan 20 at 0:29
add a comment |
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1
If I was you I'd keep reversing - there is no way that
20decimal has any direct correlation with40 0D 03 00hex. So maybe it isn't storing decimal amounts directly, maybe it's a vector or something else instead?– slugster
Jan 19 at 23:43