otool -h a1.out 
a1.out:
Mach header
      magic  cputype cpusubtype  caps    filetype ncmds sizeofcmds      flags
 0xfeedfacf 16777228          0  0x00           2    16        744 0x00200085
rajeshrao@IX-300 asm % otool -l a1.out
a1.out:
Load command 0
      cmd LC_SEGMENT_64
  cmdsize 72
  segname __PAGEZERO
   vmaddr 0x0000000000000000
   vmsize 0x0000000100000000
  fileoff 0
 filesize 0
  maxprot 0x00000000
 initprot 0x00000000
   nsects 0
    flags 0x0
Load command 1
      cmd LC_SEGMENT_64
  cmdsize 232
  segname __TEXT
   vmaddr 0x0000000100000000
   vmsize 0x0000000000004000
  fileoff 0
 filesize 16384
  maxprot 0x00000005
 initprot 0x00000005
   nsects 2
    flags 0x0
Section
  sectname __text
   segname __TEXT
      addr 0x0000000100003f75
      size 0x0000000000000033
    offset 16245
     align 2^0 (1)
    reloff 0
    nreloc 0
     flags 0x80000400
 reserved1 0
 reserved2 0
Section
  sectname __unwind_info
   segname __TEXT
      addr 0x0000000100003fa8
      size 0x0000000000000058
    offset 16296
     align 2^2 (4)
    reloff 0
    nreloc 0
     flags 0x00000000
 reserved1 0
 reserved2 0
Load command 2
      cmd LC_SEGMENT_64
  cmdsize 72
  segname __LINKEDIT
   vmaddr 0x0000000100004000
   vmsize 0x0000000000004000
  fileoff 16384
 filesize 504
  maxprot 0x00000001
 initprot 0x00000001
   nsects 0
    flags 0x0
Load command 3
      cmd LC_DYLD_CHAINED_FIXUPS
  cmdsize 16
  dataoff 16384
 datasize 56
Load command 4
      cmd LC_DYLD_EXPORTS_TRIE
  cmdsize 16
  dataoff 16440
 datasize 48
Load command 5
     cmd LC_SYMTAB
 cmdsize 24
  symoff 16496
   nsyms 4
  stroff 16560
 strsize 40
Load command 6
            cmd LC_DYSYMTAB
        cmdsize 80
      ilocalsym 0
      nlocalsym 2
     iextdefsym 2
     nextdefsym 2
      iundefsym 4
      nundefsym 0
         tocoff 0
           ntoc 0
      modtaboff 0
        nmodtab 0
   extrefsymoff 0
    nextrefsyms 0
 indirectsymoff 0
  nindirectsyms 0
      extreloff 0
        nextrel 0
      locreloff 0
        nlocrel 0
Load command 7
          cmd LC_LOAD_DYLINKER
      cmdsize 32
         name /usr/lib/dyld (offset 12)
Load command 8
     cmd LC_UUID
 cmdsize 24
    uuid 70CC305F-C3A3-3272-9E15-F393371C296D
Load command 9
      cmd LC_BUILD_VERSION
  cmdsize 32
 platform 1
    minos 15.0
      sdk n/a
   ntools 1
     tool 3
  version 1115.7.3
Load command 10
      cmd LC_SOURCE_VERSION
  cmdsize 16
  version 0.0
Load command 11
       cmd LC_MAIN
   cmdsize 24
  entryoff 16245
 stacksize 0
Load command 12
          cmd LC_LOAD_DYLIB
      cmdsize 56
         name /usr/lib/libSystem.B.dylib (offset 24)
   time stamp 2 Thu Jan  1 05:30:02 1970
      current version 1351.0.0
compatibility version 1.0.0
Load command 13
      cmd LC_FUNCTION_STARTS
  cmdsize 16
  dataoff 16488
 datasize 8
Load command 14
      cmd LC_DATA_IN_CODE
  cmdsize 16
  dataoff 16496
 datasize 0
Load command 15
      cmd LC_CODE_SIGNATURE
  cmdsize 16
  dataoff 16608
 datasize 280
rajeshrao@IX-300 asm %