old_contents: /* File.js */
  
  const EOF = -1 ;
  
  class File
  {
      constructor(core){
          this.mCore = core ;
      }
  
      getc() {
          while(true){
              let c = this.mCore.getc() ;
              if(c != null) {
                  return c ;
              }
          }
      }
  
      getl() {
          while(true){
              let c = this.mCore.getl() ;
              if(c != null) {
                  return c ;
              }
          }
      }
  }
  
  /* Global variables */
  stdin  = new File(_stdin) ;
  stdout = new File(_stdout) ;
  stderr = new File(_stderr) ;
  
new_contents: /* File.js */
  
  const EOF = -1 ;
  
  class File
  {
      constructor(core){
          this.mCore = core ;
      }
  
      getc() {
          while(true){
              let c = this.mCore.getc() ;
              if(c != null) {
                  return c ;
              }
          }
      }
  
      getl() {
          while(true){
              let c = this.mCore.getl() ;
              if(c != null) {
                  return c ;
              }
          }
      }
  
      put(str) {
          this.mCore.put(str) ;
      }
  }
  
  /* Global variables */
  stdin  = new File(_stdin) ;
  stdout = new File(_stdout) ;
  stderr = new File(_stderr) ;
  
subject: Update "File" class to add "put" method