The Linux system integrates various tools for calculating checksums, such as sha256sum and md5sum. We can use these tools to calculate the checksum of specified files, and compare the changes of the checksums before and after modifying the file. Below commands use md5sum to calculate the checksums of the hello.c file before and after modification:

$ md5sum hello.c
87cb921a75d4211a57ba747275e8bbe6 //Original MD5 checksum of hello.c
$ md5sum hello.c
79c3416910f9ea0d65a72cb720368416 //New MD5 checksum after adding one line

It can be seen that modifying just one line of code in the original file will result in greatly different MD5 checksums.