SHA512 is part of the SHA family of cryptographic hash functions, which are part of the Secure Hash Standard (SHS) specification. The SHA512 checksum (512 bits) output is represented by 128 characters in hex format. The SHA512 value is available during the download process and can be used to validate the software image.

$ sha512sum -c Download_Image.iso
Then Compare the hash (the alphanumeric string on left) that your machine calculated with the corresponding hash in the SHA512SUMS file.

Example of SHA512 checksum of a FreeBSD Software image:
$ sha512sum -c FreeBSD-11.1-RELEASE.iso

In Windows 10, use CertUtil.exe, Microsoft File Integrity Verifier.
C:\WINDOWS\System32>certutil -hashfile Path-and-File_Name
Must be “Run as Administrator

C:\WINDOWS\system32>certutil.exe -hashfile C:\Temp\FreeBSD-11.1-RELEASE.iso
SHA1 hash of C:\Temp\FreeBSD-11.1-RELEASE.iso:
CertUtil: -hashfile command completed successfully.